CustomElementRegistry.define errors due to duplicate element registration

[takaji10]

Description

When embedding the BookReader on a webpage, multiple DOMException errors appear in the browser console. This occurs because several custom elements are being registered more than once via customElements.define(). The errors don't prevent the BookReader from functioning, but they clutter the console and may mask other legitimate issues during development or debugging.
The problem can be reproduced by embedding any BookReader on a page and opening the browser's developer console.

Evidence / Screenshot (if possible)

DOMException: CustomElementRegistry.define: 'ia-activity-indicator' has already been defined as a custom element DOMException: CustomElementRegistry.define: 'ia-icon-close' has already been defined as a custom element DOMException: CustomElementRegistry.define: 'modal-template' has already been defined as a custom element DOMException: CustomElementRegistry.define: 'modal-manager' has already been defined as a custom element DOMException: CustomElementRegistry.define: 'iaux-in-share-panel' has already been defined as a custom element DOMException: CustomElementRegistry.define: 'iaux-in-sort-files-button' has already been defined as a custom element DOMException: CustomElementRegistry.define: 'iaux-in-viewable-files-panel' has already been defined as a custom element

Stack traces point to multiple modules (modal-manager.mjs, share-panel.js, viewable-files.js, ia-book-actions, etc.) each attempting to register the same custom elements.

Expectation

The BookReader should load without throwing console errors. Each custom element should only be registered once, with subsequent registration attempts gracefully skipped.

Context

Operating system: Windows 11
Browser: Firefox 147.0.1 (also reproducible in Chrome)
BookReader version: 5.0.0-106 (per stack trace)

Proposal & Constraints

Wrap customElements.define() calls with an existence check before registration:
if (!customElements.get('element-name')) { customElements.define('element-name', ElementClass); }

Stakeholders

Unknown