fix(calendar): don't allow RDATE unless already defined

Since RDATE are not properly supported in EAS, hide the possibility to
specify recurring dates unless the component being edited already
contains RDATE(s).

UI/Templates/SchedulerUI/UIxCalMainView.wox

@@ -14,6 +14,7 @@
     var dayStartHour = <var:string value="dayStartHour"/>;
     var currentView = '<var:string value="currentView"/>';
     var localeCode = '<var:string value="localeCode" />';
+    var repeatFrequencies = <var:string value="repeatFrequencies.jsonRepresentation" />;
     var centerIsClose = <var:string value="listIsCollapsed.jsonRepresentation" />;
   </script>
   <var:component className="UIxCalendarSelector" />