Ticket #13470: pixel-sanity-check.13470.diff

wp-admin/js/nav-menu.dev.js

@@ -55 +55 @@
                         // jQuery extensions
                         $.fn.extend({
                                 menuItemDepth : function() {
-                                        return api.pxToDepth( this.eq(0).css('margin-left').slice(0, -2) );
+                                        var margin = this.eq(0).css('margin-left');
+                                        return api.pxToDepth( margin && -1 != margin.indexOf('px') ? margin.slice(0, -2) : 0 );
                                 },
                                 updateDepthClass : function(current, prev) {
                                         return this.each(function(){