Fixes select2#2434 Tagging support allows creation of tags that are only whitespace

Author: sbilstein

select2.js

@@ -2953,7 +2953,7 @@ the specific language governing permissions and limitations under the Apache Lic
         // multi
         onSelect: function (data, options) {
 
-            if (!this.triggerSelect(data)) { return; }
+            if (!this.triggerSelect(data) || data.text === "") { return; }
 
             this.addSelectedChoice(data);