Merge pull request select2#2287 from eduardojmatos/master

Testing if the dropdown is opened before call positionDropdown

Author: kevin-brown

select2.js

@@ -1396,7 +1396,7 @@ the specific language governing permissions and limitations under the Apache Lic
             var that = this;
             this.container.parents().add(window).each(function () {
                 $(this).on(resize+" "+scroll+" "+orient, function (e) {
-                    that.positionDropdown();
+                    if (that.opened()) that.positionDropdown();
                 });
             });