Fix accordion change event to ensure it only triggers for fluent-accordion elements (#4600)

Author: dvoituron

src/Core.Scripts/src/FluentUICustomEvents.ts

@@ -14,6 +14,12 @@ export namespace Microsoft.FluentUI.Blazor.FluentUICustomEvents {
     blazor.registerCustomEventType('accordionchange', {
       browserEventName: 'change',
       createEventArgs: event => {
+
+        const isAccordion = event.target instanceof Element && event.target.tagName.toLowerCase() === 'fluent-accordion';
+        if (!isAccordion) {
+          return null;
+        }
+
         const item: any = event.target.accordionItems[event.target.activeItemIndex];
         const header = item?.querySelector(`[slot="heading"]`)?.innerText ?? null;
         return {