smpp_mirror: Initialize rc when cmd_id is not DELIVER_SM

Fixes: Coverity CID 1042369
diff --git a/openbsc/src/utils/smpp_mirror.c b/openbsc/src/utils/smpp_mirror.c
index 59e341d..488c4a1 100644
--- a/openbsc/src/utils/smpp_mirror.c
+++ b/openbsc/src/utils/smpp_mirror.c
@@ -170,6 +170,8 @@
 		rc = smpp_handle_deliver(esme, msg);
 		break;
 	default:
+		LOGP(DSMPP, LOGL_NOTICE, "unhandled case %d\n", cmd_id);
+		rc = 0;
 		break;
 	}