a tweak to prevent clicks propagating through the mask on IE9. select2#1058

Author: ivaynberg

select2.js

@@ -1219,7 +1219,7 @@ the specific language governing permissions and limitations under the Apache Lic
                 mask.attr("id","select2-drop-mask").attr("class","select2-drop-mask");
                 mask.hide();
                 mask.appendTo(this.body());
-                mask.on("mousedown touchstart", function (e) {
+                mask.on("mousedown touchstart click", function (e) {
                     var dropdown = $("#select2-drop"), self;
                     if (dropdown.length > 0) {
                         self=dropdown.data("select2");