fix(combo): disable UX click for checkbox in combo #10838

Author: Lipata

projects/igniteui-angular/src/lib/combo/combo-item.component.html

@@ -1,4 +1,5 @@
 <ng-container *ngIf="!isHeader && !singleMode">
-    <igx-checkbox [checked]="selected" [disableRipple]="true" [disableTransitions]="disableTransitions" [tabindex]="-1" (click)="disableCheck($event)" class="igx-combo__checkbox"></igx-checkbox>
+    <!-- checkbox should not allow changing its state from UI click (that's why it should be readonly=true), becasue when cancelling the selectionChange event in the combo, then checkbox will still change state.-->
+    <igx-checkbox [checked]="selected" [readonly]="true" [disableRipple]="true" [disableTransitions]="disableTransitions" [tabindex]="-1" (click)="disableCheck($event)" class="igx-combo__checkbox"></igx-checkbox>
 </ng-container>
 <span class="igx-drop-down__inner"><ng-content></ng-content></span>