fix: missing terminator in two value_string arrays

iu_event_type_names[] and auth_action_names[] lacked a { 0, NULL }.

Change-Id: I2e3f271b887e711c8139fbaa32410c16e7fe9921
diff --git a/openbsc/src/libiu/iu.c b/openbsc/src/libiu/iu.c
index 87a02d8..c15c6c5 100644
--- a/openbsc/src/libiu/iu.c
+++ b/openbsc/src/libiu/iu.c
@@ -95,6 +95,7 @@
 	IU_EVT_STR(IU_EVENT_IU_RELEASE),
 	IU_EVT_STR(IU_EVENT_LINK_INVALIDATED),
 #undef IU_EVT_STR
+	{ 0, NULL }
 };
 
 struct ue_conn_ctx *ue_conn_ctx_alloc(struct osmo_sccp_link *link, uint32_t conn_id)