Use zalloc rather than malloc and manually setting members to 0

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/src/clipboard.c b/src/clipboard.c
index 5a3a02d..dbd8c9b 100644
--- a/src/clipboard.c
+++ b/src/clipboard.c
@@ -214,9 +214,10 @@
 	struct wl_event_loop *loop =
 		wl_display_get_event_loop(seat->compositor->wl_display);
 
-	client = malloc(sizeof *client);
+	client = zalloc(sizeof *client);
+	if (client == NULL)
+		return;
 
-	client->offset = 0;
 	client->source = source;
 	source->refcount++;
 	client->event_source =