keyword: fix customProperties property-getter in lib

process/Keyword_lib/process.js

@@ -392,6 +392,8 @@ function KeywordUtils(){
 
         _getPropForKeyFn = function(key, field, isCustom) {
             var keyObject;
+            if (valueContainer[key] == undefined)
+                return undefined;
             if (isCustom)
                 keyObject = valueContainer[key]["customProperties"];
             else