Index: wp-admin/includes/class-walker-nav-menu-edit.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- wp-admin/includes/class-walker-nav-menu-edit.php	(revision 1ebff5d223304ed2c0b4c732a6bc4d5c26450abf)
+++ wp-admin/includes/class-walker-nav-menu-edit.php	(revision )
@@ -78,8 +78,7 @@
 		} elseif ( 'post_type' == $item->type ) {
 			$original_object = get_post( $item->object_id );
 			$original_title = get_the_title( $original_object->ID );
-		} elseif ( 'post_type_archive' == $item->type ) {
-			$original_object = get_post_type_object( $item->object );
+		} elseif ( 'post_type_archive' == $item->type && ( $original_object = get_post_type_object( $item->object ) ) ) {
 			$original_title = $original_object->labels->archives;
 		}