Add user check

src/Views/manage_lockups.php

@@ -62,7 +62,7 @@
                 <tr>
                     <td><?php echo $lockup->id; ?></td>
                     <td><a href="<?php echo $lockup->getPreviewURL(); ?>"><?php echo $lockup->getName(); ?></a></td>
-                    <td><?php echo $lockup->user->username; ?></td>
+                    <td><?php echo !empty($lockup->user) ? $lockup->user->username: 'Unknown'; ?></td>
                     <td><?php echo $lockup->date_created;?></td>
                     <td><?php echo $lockup->getApproverName(); ?></td>
                     <td><?php echo $lockup->getFullStatusText(); ?></td>