fix(grid): Only hide col if collist.length>0 #6593

Author: Vasil Mihalkov

projects/igniteui-angular/src/lib/grids/grid/grid.component.ts

@@ -655,7 +655,7 @@ export class IgxGridComponent extends IgxGridBaseComponent implements IGridDataB
     }
 
     private _setGroupColsVisibility(value) {
-        if (this.columnList && !this.hasColumnLayouts) {
+        if (this.columnList.length > 0 && !this.hasColumnLayouts) {
             this.groupingExpressions.forEach((expr) => {
                 const col = this.getColumnByName(expr.fieldName);
                 col.hidden = value;
@@ -916,7 +916,7 @@ export class IgxGridComponent extends IgxGridBaseComponent implements IGridDataB
     public ngDoCheck(): void {
         if (this.groupingDiffer && this.columnList && !this.hasColumnLayouts) {
             const changes = this.groupingDiffer.diff(this.groupingExpressions);
-            if (changes && this.columnList) {
+            if (changes && this.columnList.length > 0) {
                 changes.forEachAddedItem((rec) => {
                     const col = this.getColumnByName(rec.item.fieldName);
                     col.hidden = true;