Clear PMS selectize when dropdown opens

data/interfaces/default/settings.html

@@ -1861,6 +1861,9 @@ $(document).ready(function() {
             $('#pms_url_manual').prop('checked', false);
             $('#pms_url').val('Please verify your server above to retrieve the URL');
             PMSCloudCheck();
+        },
+        onDropdownOpen: function() {
+            this.clear();
         }
     });
     var select_pms = $select_pms[0].selectize;

data/interfaces/default/welcome.html

@@ -374,6 +374,9 @@ $(document).ready(function() {
                 $('#pms_is_remote_checkbox').prop('disabled', false);
                 $('#pms_ssl_checkbox').prop('disabled', false);
             }
+        },
+        onDropdownOpen: function() {
+            this.clear();
         }
     });
     var select_pms = $select_pms[0].selectize;