db_flatstore: free result before returning null on no more pkg

- partial allocation when doing an incomplete new connection

(cherry picked from commit 74743d6ef3bf74c1226ba5a1b6bebfbe19b06b93)
(cherry picked from commit 386ef2f61d18966ceb70916869389f2690e0a6ef)

modules/db_flatstore/km_flat_con.c

@@ -115,6 +115,7 @@ struct flat_con* flat_new_connection(struct flat_id* id)
 	fn = get_name(id);
 	if (fn==0){
 		LM_ERR("get_name() failed\n");
+		pkg_free(res);
 		return 0;
 	}