Check for osmo_fsm_register() error return value

Change-Id: Idbc1557739b2a253b73914e6f1f18a6d169d882e
diff --git a/tests/fsm/fsm_dealloc_test.c b/tests/fsm/fsm_dealloc_test.c
index 9a6974d..48f80e5 100644
--- a/tests/fsm/fsm_dealloc_test.c
+++ b/tests/fsm/fsm_dealloc_test.c
@@ -452,7 +452,7 @@
 
 	log_set_category_filter(osmo_stderr_target, DLGLOBAL, 1, LOGL_DEBUG);
 
-	osmo_fsm_register(&test_fsm);
+	OSMO_ASSERT(osmo_fsm_register(&test_fsm) == 0);
 
 	test_osmo_fsm_term_safely();
 	test_osmo_fsm_set_dealloc_ctx();