feat(query-builder): don't show inner tree if not in edit mode and no conditions

Author: igdmdimitrov

projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.html

@@ -459,7 +459,9 @@ <h6 class="igx-filter-empty__title">
             </div>
         </div>
 
-        <ng-container *ngIf="(!expressionItem.inEditMode && expressionItem.expression.searchTree) || (expressionItem.inEditMode && selectedField?.filters?.condition(selectedCondition)?.isNestedQuery)">
+        <ng-container *ngIf="
+            (!expressionItem.inEditMode && expressionItem.expression.searchTree && expressionItem.expression.searchTree.filteringOperands?.length > 0) ||
+            (expressionItem.inEditMode && selectedField?.filters?.condition(selectedCondition)?.isNestedQuery)">
             <igx-query-builder-tree
                 [style.display]="expressionItem.inEditMode || expressionItem.expanded ? 'block' : 'none'"
                 [entities]="entities"