fix invalid func in nested query

src/client/src/tscSQLParser.c

@@ -8092,6 +8092,10 @@ static int32_t getTableNameFromSubquery(SSqlNode* pSqlNode, SArray* tableNameLis
     int32_t num = (int32_t)taosArrayGetSize(sub->pSubquery);
     for (int32_t i = 0; i < num; ++i) {
       SSqlNode* p = taosArrayGetP(sub->pSubquery, i);
+      if (p->from == NULL) {
+        return TSDB_CODE_TSC_INVALID_OPERATION;
+      }
+      
       if (p->from->type == SQL_NODE_FROM_TABLELIST) {
         int32_t code = getTableNameFromSqlNode(p, tableNameList, msgBuf, pSql);
         if (code != TSDB_CODE_SUCCESS) {