Silent a warning from coverity about icmap_track being used without assign

Signed-off-by: Steven Dake <sdake@redhat.com>
Reviewed-by: Angus Salkeld <asalked@redhat.com>

exec/cmap.c

@@ -507,7 +507,7 @@ static void message_handler_req_lib_cmap_track_add(void *conn, const void *messa
 	struct res_lib_cmap_track_add res_lib_cmap_track_add;
 	cs_error_t ret;
 	cmap_track_handle_t handle = 0;
-	icmap_track_t track;
+	icmap_track_t track = NULL;
 	icmap_track_t *hdb_track;
 	struct cmap_track_user_data *cmap_track_user_data;
 	const char *key_name;