fix: return -1 if child table's uid not exist

source/dnode/vnode/src/meta/metaTable.c

@@ -532,6 +532,9 @@ static int metaDropTableByUid(SMeta *pMeta, tb_uid_t uid, int *type) {
   SDecoder   dc = {0};
 
   rc = tdbTbGet(pMeta->pUidIdx, &uid, sizeof(uid), &pData, &nData);
+  if (rc < 0) {
+    return -1;
+  }
   int64_t version = ((SUidIdxVal *)pData)[0].version;
 
   tdbTbGet(pMeta->pTbDb, &(STbDbKey){.version = version, .uid = uid}, sizeof(STbDbKey), &pData, &nData);