app: fixed av when asynccall already freed

src/base/fresnel.forms.pas

@@ -878,6 +878,7 @@ end;
 
 procedure TFresnelBaseApplication.DoHandleAsyncCalls;
 begin
+  if FAsyncCall=nil then exit;
   FAsyncCall.ProcessQueue;
 end;
 

src/fresnel.app.pas

@@ -250,7 +250,6 @@ begin
   ProcessAsyncCallQueue;
   UnregisterFindGlobalComponentProc(@FindApplicationComponent);
 
-
   inherited Destroy;
 
   Include(FFlags,AppDoNotCallAsyncQueue);