[evolution/evolution-3-12] cal_comp_util_compare_event_timezones: Do not ask with NULL tzid

[Milan Crha <mcrha src gnome org>]

commit 3957891cc084b43e2743003fa446f18e77e794ae
Author: Milan Crha <mcrha redhat com>
Date:   Tue Nov 4 06:52:05 2014 +0100

    cal_comp_util_compare_event_timezones: Do not ask with NULL tzid
    
    Asking an ECalClient for a timezone with NULL tzid only produces
    a runtime warning on a console.

 calendar/gui/comp-util.c |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)
---
diff --git a/calendar/gui/comp-util.c b/calendar/gui/comp-util.c
index 16dfd5d..77b31b4 100644
--- a/calendar/gui/comp-util.c
+++ b/calendar/gui/comp-util.c
@@ -150,8 +150,11 @@ cal_comp_util_compare_event_timezones (ECalComponent *comp,
                /* If the TZIDs differ, we have to compare the UTC offsets
                 * of the start and end times, using their own timezones and
                 * the given timezone. */
-               e_cal_client_get_timezone_sync (
-                       client, start_datetime.tzid, &start_zone, NULL, NULL);
+               if (start_datetime.tzid)
+                       e_cal_client_get_timezone_sync (client, start_datetime.tzid, &start_zone, NULL, NULL);
+               else
+                       start_zone = NULL;
+
                if (start_zone == NULL)
                        goto out;
 
@@ -168,8 +171,11 @@ cal_comp_util_compare_event_timezones (ECalComponent *comp,
                                goto out;
                }
 
-               e_cal_client_get_timezone_sync (
-                       client, end_datetime.tzid, &end_zone, NULL, NULL);
+               if (end_datetime.tzid)
+                       e_cal_client_get_timezone_sync (client, end_datetime.tzid, &end_zone, NULL, NULL);
+               else
+                       end_zone = NULL;
+
                if (end_zone == NULL)
                        goto out;