[gnome-calendar] Prevent crash clicking on the "New Event" button

[Bastien Nocera <hadess src gnome org>]

commit 604e4ce4381a576df707abec9993eecc8902b4b2
Author: Bastien Nocera <hadess hadess net>
Date:   Thu Dec 6 09:19:42 2012 +0100

    Prevent crash clicking on the "New Event" button

 src/gcal-view.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/gcal-view.c b/src/gcal-view.c
index 78f3ee7..00134bc 100644
--- a/src/gcal-view.c
+++ b/src/gcal-view.c
@@ -180,5 +180,7 @@ gcal_view_create_event_on_current_unit (GcalView *view)
 {
   g_return_if_fail (GCAL_IS_VIEW (view));
 
+  g_return_if_fail (GCAL_VIEW_GET_INTERFACE (view)->create_event_on_current_unit);
+
   GCAL_VIEW_GET_INTERFACE (view)->create_event_on_current_unit (view);
 }