Merge pull request #3851 from yallups/Terminating-script-undefined-args

Fixes an issue of args === undefined and script terminates

src/js/select2/core.js

@@ -358,6 +358,10 @@ define([
       'unselect': 'unselecting'
     };
     
+    if (args === undefined) {
+      args = {};
+    }
+
     if (name in preTriggerMap) {
       var preTriggerName = preTriggerMap[name];
       var preTriggerArgs = {