[evolution] Fix an issue found by Coverity Scan introduced by a commit for bug #657808

[Milan Crha <mcrha src gnome org>]

commit 55601f56e5043ea3d86b84bd07c9a2e8a30fe467
Author: Milan Crha <mcrha redhat com>
Date:   Tue Nov 5 19:42:00 2013 +0100

    Fix an issue found by Coverity Scan introduced by a commit for bug #657808

 calendar/gui/e-calendar-selector.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/calendar/gui/e-calendar-selector.c b/calendar/gui/e-calendar-selector.c
index b588c6a..c134d29 100644
--- a/calendar/gui/e-calendar-selector.c
+++ b/calendar/gui/e-calendar-selector.c
@@ -314,11 +314,11 @@ calendar_selector_data_dropped (ESourceSelector *selector,
                                 GdkDragAction action,
                                 guint info)
 {
-       icalcomponent *icalcomp;
+       icalcomponent *icalcomp = NULL;
        EActivity *activity;
        EShellBackend *shell_backend;
        EShellView *shell_view;
-       ESource *source;
+       ESource *source = NULL;
        ESourceRegistry *registry;
        GCancellable *cancellable;
        gchar **segments;