fix: uninitialised value while create stb

source/dnode/mnode/impl/src/mndStb.c

@@ -670,8 +670,8 @@ static int32_t mndCreateStb(SMnode *pMnode, SNodeMsg *pReq, SMCreateStbReq *pCre
     memcpy(stbObj.pAst2, pCreate->pAst2, stbObj.ast2Len);
   }
 
-  stbObj.pColumns = taosMemoryMalloc(stbObj.numOfColumns * sizeof(SSchema));
-  stbObj.pTags = taosMemoryMalloc(stbObj.numOfTags * sizeof(SSchema));
+  stbObj.pColumns = taosMemoryCalloc(1, stbObj.numOfColumns * sizeof(SSchema));
+  stbObj.pTags = taosMemoryCalloc(1, stbObj.numOfTags * sizeof(SSchema));
   if (stbObj.pColumns == NULL || stbObj.pTags == NULL) {
     terrno = TSDB_CODE_OUT_OF_MEMORY;
     return -1;