chan_alloc: After freeing set the pointer to NULL.
diff --git a/openbsc/src/chan_alloc.c b/openbsc/src/chan_alloc.c
index dda5ff2..b061fc7 100644
--- a/openbsc/src/chan_alloc.c
+++ b/openbsc/src/chan_alloc.c
@@ -272,6 +272,7 @@
 		if (lchan->conn) {
 			LOGP(DRLL, LOGL_ERROR, "lchan->conn should be NULL.\n");
 			subscr_con_free(lchan->conn);
+			lchan->conn = NULL;
 		}
 	} else {
 		struct challoc_signal_data sig;