Issue when trying to update clients info - php

Question

I'm having an issue where when I go to upload or update a client, it will automatically take the clients profile off if you do not add an image to upload. But If I just want to update their website or motto, and click update, I don't want to have to try and search their image down again and upload it just to update a few items. Any Ideas on why it's doing this? Thank You In Advance.
Heres my code:
<?php
//Gets The Users info when editing it.
$stmt = $DB_con->prepare('SELECT * FROM sponsors WHERE id='.$id);
$stmt->execute();
if($stmt->rowCount() > 0)
{
$row=$stmt->fetch(PDO::FETCH_ASSOC);
extract($row);
}
?>
<div class="col-xs-12 col-sm-6 col-md-8">
<form method="post" class="form-horizontal" enctype="multipart/form-data">
<div class="form-group">
<label for="sponsor_name" class="col-sm-3 control-label">Sponsor Name:</label>
<div class="col-sm-9">
<input type="text" class="form-control" name="sponsor_name" id="sponsor_name" value="<?php echo $name;?>">
</div>
</div>
<div class="form-group">
<label for="sponsor_phone" class="col-sm-3 control-label">Sponsor Phone Number:</label>
<div class="col-sm-9">
<input type="text" class="form-control" name="sponsor_phone" id="sponsor_phone" value="<?php echo $phone;?>">
</div>
</div>
<div class="form-group">
<label for="sponsor_moto" class="col-sm-3 control-label">Sponsors Motto:</label>
<div class="col-sm-9">
<input type="text" class="form-control" name="sponsor_motto" id="sponsor_motto" value="<?php echo $motto;?>">
</div>
</div>
<div class="form-group">
<label for="sponsors_website" class="col-sm-3 control-label">Sponsors Website:</label>
<div class="col-sm-9">
<input type="text" class="form-control" name="sponsor_website" id="sponsor_website" value="<?php echo $website;?>">
</div>
</div>
<div class="form-group">
<label for="sponsor_on" class="col-sm-3 control-label">Sponsor on or off?:</label>
<div class="col-sm-9">
<input type="text" class="form-control" name="sponsor_on" id="sponsor_on" value="<?php echo $live;?>">
</div>
</div>
<div class="form-group">
<label for="image" class="col-sm-3 control-label"> Profile Picture </label>
<div class="col-sm-9">
<p><img id="image" src="../images/sponsors/<?php echo $row['logo'];?>" height="150" width="150" /></p>
<div class="col-sm-9">
<input class="input-group" type="file" name="user_image" accept="image/*" />
</div>
<br>
<br>
<div class="col-sm-offset-3 col-sm-9">
<button type="submit" name="btn_save_updates" class="btn btn-info waves-effect waves-light">Update Sponsor</button>
Delete Sponsor</button>
</div>
</div>
</div>
</form>
Heres my PHP code that will update the Database.
<?php
if(isset($_GET['edit_id']) && !empty($_GET['edit_id']))
{
$id = $_GET['edit_id'];
$stmt_edit = $DB_con->prepare('SELECT * FROM sponsors WHERE id =:uid');
$stmt_edit->execute(array(':uid'=>$id));
$edit_row = $stmt_edit->fetch(PDO::FETCH_ASSOC);
extract($edit_row);
}
else
{
header("Location: ../../login.php");
}
if(isset($_POST['btn_save_updates']))
{
$username = $_POST['user_name'];
$description = $_POST['description'];
$imgFile = $_FILES['user_image']['name'];
$tmp_dir = $_FILES['user_image']['tmp_name'];
$imgSize = $_FILES['user_image']['size'];
if($imgFile)
{
$upload_dir = '../images/sponsors/';
$imgExt = strtolower(pathinfo($imgFile,PATHINFO_EXTENSION));
$valid_extensions = array('jpeg', 'jpg', 'png', 'gif');
$userprofile = rand(1000,1000000).".".$imgExt;
if(in_array($imgExt, $valid_extensions))
{
if($imgSize < 5000000)
{
unlink($upload_dir.$edit_row['logo']);
move_uploaded_file($tmp_dir,$upload_dir.$userprofile);
}
else
{
$errMSG = "Sorry, Your File Is Too Large To Upload. It Should Be Less Than 5MB.";
}
}
else
{
$errMSG = "Sorry, only JPG, JPEG, PNG & GIF Extension Files Are Allowed.";
}
}
else
{
$userprofile = $edit_row['userprofile'];
}
if(!isset($errMSG))
{
$sponsorname = $_POST['sponsor_name'];
$motto = $_POST['sponsor_motto'];
$phone = $_POST['sponsor_phone'];
$website = $_POST['sponsor_website'];
$son = $_POST['sponsor_on'];
$stmt = $DB_con->prepare('UPDATE sponsors SET name=:sname, motto=:smotto, phone=:sphone,website=:swebsite,live=:son, logo=:upic WHERE id=:uid');
$stmt->bindParam(':sname',$sponsorname);
$stmt->bindParam(':smotto',$motto);
$stmt->bindParam(':sphone',$phone);
$stmt->bindParam(':swebsite',$website);
$stmt->bindParam(':son',$son);
$stmt->bindParam(':upic',$userprofile);
$stmt->bindParam(':uid',$id);
if($stmt->execute()){
?>
<script>
alert('Successfully Updated...');
window.location.href='managesponsors.php?action=sponsorupdated';
</script>
<?php
}
else{
$errMSG = "Sorry User Could Not Be Updated!";
}
}
}
?>