[gnome-calendar] event-widget: Handle NULL in event sorting

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 5f4c5f5cbeea6cb2d04c34716160a5425bb5784a
Author: Elias Entrup <elias-git flump de>
Date:   Tue Feb 6 12:25:47 2018 +0100

    event-widget: Handle NULL in event sorting
    
    The application crashes when e_cal_component_get_last_modified
    returns NULL which is used for sorting events.

 src/gcal-event-widget.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)
---
diff --git a/src/gcal-event-widget.c b/src/gcal-event-widget.c
index ba7b7f75..903d24dd 100644
--- a/src/gcal-event-widget.c
+++ b/src/gcal-event-widget.c
@@ -18,8 +18,9 @@
 
 #define G_LOG_DOMAIN "GcalEventWidget"
 
-#include <string.h>
+#include <libecal/libecal.h>
 #include <glib/gi18n.h>
+#include <string.h>
 
 #include "gcal-event-widget.h"
 #include "gcal-utils.h"
@@ -1167,11 +1168,11 @@ gint
 gcal_event_widget_sort_events (GcalEventWidget *widget1,
                                GcalEventWidget *widget2)
 {
-  g_autoptr (GDateTime) dt_time1, dt_time2;
+  g_autoptr (GDateTime) dt_time1 = NULL;
+  g_autoptr (GDateTime) dt_time2 = NULL;
   icaltimetype *ical_dt;
   gint diff;
 
-  dt_time1 = dt_time2 = NULL;
   diff = gcal_event_is_multiday (widget2->event) - gcal_event_is_multiday (widget1->event);
 
   if (diff != 0)
@@ -1188,10 +1189,12 @@ gcal_event_widget_sort_events (GcalEventWidget *widget1,
     return diff;
 
   e_cal_component_get_last_modified (gcal_event_get_component (widget1->event), &ical_dt);
-  dt_time1 = icaltime_to_datetime (ical_dt);
+  if (ical_dt)
+    dt_time1 = icaltime_to_datetime (ical_dt);
 
   e_cal_component_get_last_modified (gcal_event_get_component (widget2->event), &ical_dt);
-  dt_time2 = icaltime_to_datetime (ical_dt);
+  if (ical_dt)
+    dt_time2 = icaltime_to_datetime (ical_dt);
 
-  return g_date_time_compare (dt_time2, dt_time1);
+  return dt_time1 && dt_time2 ? g_date_time_compare (dt_time2, dt_time1) : 0;
 }