Check for osmo_fsm_register() error return value

Change-Id: Idda1a4050cf9d285225ae48a4ba6f48c04f9598b
diff --git a/src/bankd_client_fsm.c b/src/bankd_client_fsm.c
index cedb597..2e3fdc9 100644
--- a/src/bankd_client_fsm.c
+++ b/src/bankd_client_fsm.c
@@ -271,5 +271,5 @@
 
 static __attribute__((constructor)) void on_dso_load(void)
 {
-	osmo_fsm_register(&remsim_client_bankd_fsm);
+	OSMO_ASSERT(osmo_fsm_register(&remsim_client_bankd_fsm) == 0);
 }