Anonymous clients are no longer accidently disconnected from the broker after a SIGHUP.

ChangeLog.txt

@@ -15,6 +15,8 @@ Broker:
   clients that connect without a username.
 - Fix subscriptions being deleted when clients subscribed to a topic beginning
   with a $ but that is not $SYS.
+- Anonymous clients are no longer accidently disconnected from the broker
+  after a SIGHUP.
 
 Client library:
 - Fix topic matching edge case.

src/security_default.c

@@ -624,8 +624,9 @@ int mosquitto_unpwd_check_default(struct mosquitto_db *db, const char *username,
 	int rc;
 #endif
 
-	if(!db || !username) return MOSQ_ERR_INVAL;
+	if(!db) return MOSQ_ERR_INVAL;
 	if(!db->unpwd) return MOSQ_ERR_SUCCESS;
+	if(!username) return MOSQ_ERR_INVAL; /* Check must be made only after checking db->unpwd. */
 
 	HASH_ITER(hh, db->unpwd, u, tmp){
 		if(!strcmp(u->username, username)){