fix(uiSelectMultiple): $select.refreshItems is not a function

Resolves exception:

TypeError: $select.refreshItems is not a function at 
uis.directive.$timeout.controller.ctrl.refreshComponent 

when the select is multiple (v 18.0 & master)

Author: robinComa

src/uiSelectMultipleDirective.js

@@ -26,8 +26,12 @@ uis.directive('uiSelectMultiple', ['uiSelectMinErr','$timeout', function(uiSelec
         //Remove already selected items
         //e.g. When user clicks on a selection, the selected array changes and
         //the dropdown should remove that item
-        $select.refreshItems();
-        $select.sizeSearchInput();
+        if($select.refreshItems){
+          $select.refreshItems();
+        }
+        if($select.sizeSearchInput){
+          $select.sizeSearchInput();
+        }
       };
 
       // Remove item from multiple select