fixed start page button flickering - fixes #4298

tabby-core/src/components/startPage.component.pug

@@ -5,7 +5,7 @@ div
 
     .list-group
         a.list-group-item.list-group-item-action.d-flex(
-            *ngFor='let button of getButtons()',
+            *ngFor='let button of getButtons(); trackBy: buttonsTrackBy',
             (click)='button.click()',
         )
             .d-flex.align-self-center([innerHTML]='sanitizeIcon(button.icon)')

tabby-core/src/components/startPage.component.ts

@@ -32,4 +32,8 @@ export class StartPageComponent {
     sanitizeIcon (icon?: string): any {
         return this.domSanitizer.bypassSecurityTrustHtml(icon ?? '')
     }
+
+    buttonsTrackBy (btn: ToolbarButton): any {
+        return btn.title + btn.icon
+    }
 }