 				{
 					customConvert = function(item:*):String
 					{
+						if (item === undefined || item === null) return "";
 						return item[fieldName].toString().toLocaleLowerCase();
 					}
 				}

			_indexMap.clear();
			if (returnIndexedArray)
			{
				/* Assert that this is an object array, this won't necessarily work with primitive types. */
				if (!arrayIsType(array, Object)) JS.error("Warning: Can't do an indexed array sort of non-objects reliably.");
				array.forEach(function(item:*, index:int):void {_indexMap.set(item, index);})
			}


				{
					customConvert = function(item:*):String
					{
						if (item === undefined || item === null) return "";
						return item[fieldName].toString();
					}
				}
