fix(query): fix leastsquares c0+null and also group by output has empty

result

TD-16136

source/libs/function/src/builtinsimpl.c

@@ -1754,6 +1754,11 @@ int32_t leastSQRFunction(SqlFunctionCtx* pCtx) {
       }
       break;
     }
+    case TSDB_DATA_TYPE_NULL: {
+      GET_RES_INFO(pCtx)->isNullRes = 1;
+      numOfElem = 1;
+      break;
+    }
 
     default:
       break;
@@ -1797,7 +1802,7 @@ int32_t leastSQRFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
   size_t len = snprintf(varDataVal(buf), sizeof(buf) - VARSTR_HEADER_SIZE, "{slop:%.6lf, intercept:%.6lf}", param[0][2], param[1][2]);
   varDataSetLen(buf, len);
 
-  colDataAppend(pCol, currentRow, buf, false);
+  colDataAppend(pCol, currentRow, buf, pResInfo->isNullRes);
 
   return pResInfo->numOfRes;
 }