fix: c is uninitialized for empty btree

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

@@ -309,7 +309,7 @@ int metaAlterSTable(SMeta *pMeta, int64_t version, SVCreateStbReq *pReq) {
   int64_t     oversion;
   SDecoder    dc = {0};
   int32_t     ret;
-  int32_t     c;
+  int32_t     c = -2;
 
   tdbTbcOpen(pMeta->pUidIdx, &pUidIdxc, &pMeta->txn);
   ret = tdbTbcMoveTo(pUidIdxc, &pReq->suid, sizeof(tb_uid_t), &c);