fix(game-events): icon animation null instance handler (#889)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Bug Fixes**
- Improved error handling in the Game Events Monitor Footer by
preventing runtime errors related to undefined button icons.
- Updated button icon behavior to avoid animation when icons are not
defined, enhancing user experience.

- **Tests**
- Modified test cases to reflect new behavior of button icons, focusing
on animation rather than error throwing.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

app/components/pages/game/GamePlaying/GameEventsMonitor/GameEventsMonitorFooter/GameEventsMonitorFooter.vue

@@ -115,22 +115,20 @@ function onClickFromPreviousEventButton(): void {
   if (!canGoToPreviousGameEvent.value) {
     return;
   }
-  if (!previousEventButtonIcon.value) {
-    throw createError("Previous Event Button Icon is not defined");
-  }
   goToPreviousGameEvent();
-  void animateElementOnce(previousEventButtonIcon.value.$el as HTMLElement, "headShake");
+  if (previousEventButtonIcon.value) {
+    void animateElementOnce(previousEventButtonIcon.value.$el as HTMLElement, "headShake");
+  }
 }
 
 async function onClickFromSkipCurrentEventButton(): Promise<void> {
   if (!canGoToNextGameEvent.value) {
     return;
   }
-  if (!skipCurrentEventButtonIcon.value) {
-    throw createError("Skip Current Event Button Icon is not defined");
-  }
   await goToNextGameEvent();
-  void animateElementOnce(skipCurrentEventButtonIcon.value.$el as HTMLElement, "headShake");
+  if (skipCurrentEventButtonIcon.value) {
+    void animateElementOnce(skipCurrentEventButtonIcon.value.$el as HTMLElement, "headShake");
+  }
 }
 
 watch(() => keyboard.value.arrowRight.isPressed, (isKeyPressed: boolean) => {