Fix selection of calendar in event/task editors

Fixes #3049
Fixes #3050

UI/Scheduler/UIxComponentEditor.m

@@ -1428,7 +1428,8 @@ iRANGE(2);
 
 - (void) setComponentCalendar: (SOGoAppointmentFolder *) _componentCalendar
 {
-  ASSIGN(componentCalendar, _componentCalendar);
+  if (_componentCalendar)
+    ASSIGN(componentCalendar, _componentCalendar);
 }
 
 /* priorities */

UI/Templates/SchedulerUI/UIxAppointmentEditor.wox

@@ -8,6 +8,7 @@
   xmlns:rsrc="OGo:url"
   xmlns:label="OGo:label"
   className="UIxComponentEditor"
+  componentCalendar="componentCalendar"
   eventIsReadOnly="eventIsReadOnly"
   var:component="event"
   var:rsvpURL="rsvpURL"

UI/Templates/SchedulerUI/UIxTaskEditor.wox

@@ -8,6 +8,7 @@
   xmlns:rsrc="OGo:url"
   xmlns:label="OGo:label"
   className="UIxComponentEditor"
+  componentCalendar="componentCalendar"
   eventIsReadOnly="eventIsReadOnly"
   var:component="todo"
   var:saveURL="saveURL">