refactor: do some internal refactor.

source/libs/executor/src/executil.c

@@ -571,6 +571,10 @@ SExprInfo* createExprInfo(SNodeList* pNodeList, SNodeList* pGroupKeys, int32_t*
   }
 
   *numOfExprs = numOfFuncs + numOfGroupKeys;
+  if (*numOfExprs == 0) {
+    return NULL;
+  }
+
   SExprInfo* pExprs = taosMemoryCalloc(*numOfExprs, sizeof(SExprInfo));
 
   for (int32_t i = 0; i < (*numOfExprs); ++i) {

source/libs/executor/src/sortoperator.c

@@ -152,7 +152,7 @@ SSDataBlock* loadNextDataBlock(void* param) {
 void applyScalarFunction(SSDataBlock* pBlock, void* param) {
   SOperatorInfo*     pOperator = param;
   SSortOperatorInfo* pSort = pOperator->info;
-  if (pOperator->exprSupp.pExprInfo != NULL) {
+  if (pOperator->exprSupp.pExprInfo != NULL && pOperator->exprSupp.numOfExprs > 0) {
     int32_t code = projectApplyFunctions(pOperator->exprSupp.pExprInfo, pBlock, pBlock, pOperator->exprSupp.pCtx,
                                          pOperator->exprSupp.numOfExprs, NULL);
     if (code != TSDB_CODE_SUCCESS) {