--- web/js/zul/inp/ComboWidget.src.js.orig	2015-04-24 11:41:18.000000000 +0200
+++ web/js/zul/inp/ComboWidget.src.js	2015-04-24 11:42:07.000000000 +0200
@@ -182,8 +182,10 @@
 		jq(pp).addClass(this.$s('open'));
 	},
 	_checkPopupPosition: function () {
-		var pp = this.getPopupNode_(),
-			$pp = zk(pp),
+		var pp = this.getPopupNode_();
+		if (pp == null)
+			return false;
+		var $pp = zk(pp),
 			inp = this.getInputNode(),
 			ppDim = $pp.dimension(true),
 			inpDim = zk(inp).dimension(true),