Prevent NULL derefencing and accessing of freed memory.

src/read_handle_server.c

@@ -481,6 +481,7 @@ int mqtt3_handle_connect(struct mosquitto_db *db, struct mosquitto *context)
 			found_context->ws_context = context->ws_context;
 			found_context->sock = WEBSOCKET_CLIENT;
 			context->wsi = NULL;
+			context->ws_context = NULL;
 			context->sock = INVALID_SOCKET;
 
 			/* This is a hack to allow us to update the wsi->user_space

src/subs.c

@@ -97,7 +97,7 @@ static int _subs_process(struct mosquitto_db *db, struct _mosquitto_subhier *hie
 		}
 	}
 	while(source_id && leaf){
-		if(leaf->context->is_bridge && !strcmp(leaf->context->id, source_id)){
+		if(!leaf->context->id || (leaf->context->is_bridge && !strcmp(leaf->context->id, source_id))){
 			leaf = leaf->next;
 			continue;
 		}