Please help me removing this required field

hi friends,

can someone help me?
In my adminpanel, I have an page to edit my posts.
here is an screenshot:


The problem is that, If I want to change the date values only, I cant do It, because appears the error "Please select a Thumbnail Picture first".

Can you please help me fix that? So I can change the date without sending a new thumbnail? I dont have any php knowledge

Here goes my page code:

<?
    ini_set("register_globals", 1);
    ini_set("session.bug_compat_42", "Off");
    ini_set("session.bug_compat_warn", "Off");
    session_start();
    if(!empty($_SESSION['login_status']))
    {
        include("../lib/globals.php");
        $dbc=mysql_connect($host,$username,$password) or die('Unable to connect to the database...');
        mysql_select_db($dbname) or die('Unable to select the database...');

        $id=(isset($_REQUEST['id']))?$_REQUEST['id']:0;
        $s=$_REQUEST['s'];
        
        $query="select * from thon_post where id='$id'";
        $result=mysql_query($query);
        if($result)
        {
            $r=mysql_fetch_array($result);
            
            $str_dt=$r['start_date'];
            $arr=explode('-',$str_dt);
            $str_dt1=date('j-M-Y',mktime(0,0,0,$arr[1],$arr[2],$arr[0]));
            
            $path="../uploaded/".$r['picture'];
            $currentimagesize=getimagesize($path);
            $image_width=$currentimagesize[0];
            $image_height=$currentimagesize[1];
            
            if(($image_height>117.63) || ($image_width>140))
            {
                if($image_height>117.63)
                {
                    $f1=(double)(117.63/$image_height);
                    $width=$image_width*$f1;
                    $height=117.63;
                }
                if($image_width>140)
                {
                    $f2=(double)(140/$image_width);
                    $height=$image_height*$f2;
                    $width=140;
                }
            }
            else
            {
                $width=$image_width;
                $height=$image_height;
            }
        }
        
        if(isset($_POST['submit']))
        {
            $st_dt=$_POST['start_date'];
            if($st_dt!='')
            {
            
            $arr=explode('-',$st_dt);
            if($arr[0]<10)
            {
                $day='0'.$arr[0];
            }
            else
            {
                $day=$arr[0];
            }
            switch($arr[1])
            {
                case 'Jan':
                    $mon='01';
                    break;
                case 'Feb':
                    $mon='02';
                    break;
                case 'Mar':
                    $mon='03';
                    break;
                case 'Apr':
                    $mon='04';
                    break;
                case 'May':
                    $mon='05';
                    break;
                case 'Jun':
                    $mon='06';
                    break;
                case 'Jul':
                    $mon='07';
                    break;
                case 'Aug':
                    $mon='08';
                    break;
                case 'Sep':
                    $mon='09';
                    break;
                case 'Oct':
                    $mon='10';
                    break;
                case 'Nov':
                    $mon='11';
                    break;
                case 'Dec':
                    $mon='12';
                    break;
            }
            
            $start_date=$arr[2]."-".$mon."-".$day;
            
            }
            else
            {
            
            $start_date=date('Y-m-d');
            
            }

            $thumb_pic=$_FILES['thumb_pic']['name'];
            $arr1=explode('.',$thumb_pic);
            $img1=date('ymdhis')."t.".$arr1[1];
            $dest1="../uploaded/".$img1;
            $val1_1=move_uploaded_file($_FILES['thumb_pic']['tmp_name'],$dest1);
            $qry="update thon_post set `picture_thumb`='$img1', `start_date`='$start_date' where id='$id'";
            $rs=mysql_query($qry);
            if($rs)
            {
?>
                <script language="javascript" type="text/javascript">
                    alert("Post information successfully updated.");
                    window.location.href='display_post1.php?s=<? echo $s; ?>'; 
                </script>
<?
            }
        }                    
?>        
<html>
<head>
<title>Thongsaroundtheworld Admin Area</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script language="JavaScript" type="text/javascript" src="../validator/datetimepicker.js"></script>
<link href="../style/style.css" rel="stylesheet" type="text/css">
<script language="javascript">
function validate()
{
    var thumb_pic=document.getElementById('thumb_pic').value;
    if(thumb_pic=='')
    {
        alert('Please select a Thumbnail Picture first.');
        document.f1.thumb_pic.focus();
        return false;
    }
    var ext=thumb_pic.substr(thumb_pic.lastIndexOf(".")).toLowerCase();
    if(ext != ".gif" && ext != ".jpeg" && ext != ".png" && ext != ".jpg") 
    {
        alert("Please select only JPG or GIF or PNG Thumbnail Picture.");
        document.f1.thumb_pic.focus();
        return false;
    }
}
</script>
</head>
<body leftmargin="0" topmargin="0">
<? include("admin_header.php"); ?>
<table align="center" width="100%" cellspacing="0" cellpadding="0" border="0" height="100%">
<tr>
<td width="175" align="left" valign="top" bgcolor="#eeeeee"><? include("left.php"); ?></td>
<td align="center" valign="top">
<br><br><br>
<form name="f1" method="post" action="edit_post1.php?id=<? echo $id; ?>&s=<? echo $s; ?>" enctype="multipart/form-data" onSubmit="return validate();">
<table border="0" cellpadding="0" cellspacing="4" align="center"><tr><td valign="top">
<table width="360" cellspacing="0" cellpadding="0" align="center" class="tab_sty1">
  <tr bgcolor="#631e5c" height="18">
    <td align="center" class="mysty1" colspan="4"><font color="#FFFFFF"><b>Edit Post</b></font></td>
  </tr>
  <tr height="10"><td colspan="4"></td></tr>
    <tr height="22"><td width="16"></td><td width="120" class="mysty1">Name</td><td width="12" class="mysty1"><b>:</b></td><td width="210" class="mysty1"><? echo $r['name']; ?></td></tr>
    <tr height="22"><td width="16"></td><td width="120" class="mysty1">Country Name</td><td width="12" class="mysty1"><b>:</b></td><td width="210" class="mysty1"><? echo $r['country_name']; ?></td></tr>
    <tr height="22"><td width="16"></td><td width="120" class="mysty1">E-mail</td><td width="12" class="mysty1"><b>:</b></td><td width="210" class="mysty1"><? echo $r['email']; ?></td></tr>
    <tr height="22"><td width="16"></td><td width="120" class="mysty1">Comment</td>
    <td width="22" class="mysty1"><b>:</b></td><td width="210" class="mysty1"><? echo $r['comment']; ?></td></tr>
    <tr height="22"><td width="16"></td><td width="120" class="mysty1">Thumbnail Picture</td><td width="12" class="mysty1"><b>:</b></td><td width="210" class="mysty1"><input type="file" name="thumb_pic" id="thumb_pic" size="20"></td></tr>
    <tr height="22"><td width="16"></td><td width="120" class="mysty1">Start Date</td><td width="12" class="mysty1"><b>:</b></td><td class="mysty1"><input name="start_date" id="start_date" type="text" size="15" value="<? echo $str_dt1; ?>" readonly=""> 
    <a href="javascript:NewCal('start_date','ddmmmyyyy',false,24)"><img src="../images/cal.gif" alt="Pick a date" width="16" height="16" border="0" align="absmiddle"></a> (Optional)</td></tr>
    <tr height="10"><td colspan="4"></td></tr>
      <tr height="18"><td align="center" colspan="4"><input name="submit" type="submit" value="Submit"></td></tr>
      <tr height="10"><td colspan="4"></td></tr>
</table>
</td><td valign="top">
<table width="148" border="0" cellpadding="0" cellspacing="0" align="center" class="tab_sty1">
<tr height="18"><td align="center" bgcolor="#631e5c"><span class="mysty1"><font color="#FFFFFF"><b>Existing Picture</b></font></span></td></tr>
<tr><td align="center" style="padding: 6px 6px 6px 6px;"><img src="<? echo $path; ?>" width="<? echo $width; ?>" height="<? echo $height; ?>"></td></tr>
</table>
<?
    if($r['picture_thumb']!='')
    {
        $path1="../uploaded/".$r['picture_thumb'];
?>    
<br>
<table width="148" border="0" cellpadding="0" cellspacing="0" align="center" class="tab_sty1">
<tr height="18"><td align="center" bgcolor="#631e5c"><span class="mysty1"><font color="#FFFFFF"><b>Thumbnail Picture</b></font></span></td></tr>
<tr><td align="center" style="padding: 6px 6px 6px 6px;"><img src="<? echo $path1; ?>" width="88" height="88" border="1"></td></tr>
</table>
<?
    }
?>
</td>
</tr>
</table>
</form>
</td>
</td>
</tr>
</table>
</body>
</html>
<?
    }
    else
    {
        header("Location: index.php");
    }
?>

PHP:

I really appreciate If someone can help me
Thank you!

 

First you need to remove the javascript validation:

onSubmit="return validate();"

Code (markup):

After that you need to change the PHP code so when thumbnail is not posted the database not to be updated.

 

I dont have php knowledge to fix that... can you or someone help me please?