fix: Handle error when offscreen document already exists (#25138)

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## **Description**

A `try..catch` block has been added to catch errors about the Offscreen
document already existing. This circumstance is not a bug, it's expected
to happen sometimes due to race conditions between `hasDocument` and the
creation step. The code in question is just meant to create the document
if it doesn't exist, so it's OK if we get this error.

The `hasDocument` call has been removed as well, since it's now
redundant. This function wasn't safe to call anyway; it's an
undocumented private function.

See here for more information:
* https://stackoverflow.com/a/7725839
*
https://groups.google.com/a/chromium.org/g/chromium-extensions/c/D5Jg2ukyvUc4

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## **Related issues**

Fixes #25118

## **Manual testing steps**

I do not know how to test this unfortunately.

## **Screenshots/Recordings**

N/A

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

app/scripts/offscreen.js

@@ -1,3 +1,4 @@
+import { captureException } from '@sentry/browser';
 import { OffscreenCommunicationTarget } from '../../shared/constants/offscreen-communication';
 
 /**
@@ -9,29 +10,51 @@ import { OffscreenCommunicationTarget } from '../../shared/constants/offscreen-c
  */
 export async function createOffscreen() {
   const { chrome } = globalThis;
-  if (!chrome.offscreen || (await chrome.offscreen.hasDocument())) {
+  if (!chrome.offscreen) {
     return;
   }
 
+  let offscreenDocumentLoadedListener;
   const loadPromise = new Promise((resolve) => {
-    const messageListener = (msg) => {
+    offscreenDocumentLoadedListener = (msg) => {
       if (
         msg.target === OffscreenCommunicationTarget.extensionMain &&
         msg.isBooted
       ) {
-        chrome.runtime.onMessage.removeListener(messageListener);
+        chrome.runtime.onMessage.removeListener(
+          offscreenDocumentLoadedListener,
+        );
         resolve();
       }
     };
-    chrome.runtime.onMessage.addListener(messageListener);
+    chrome.runtime.onMessage.addListener(offscreenDocumentLoadedListener);
   });
 
-  await chrome.offscreen.createDocument({
-    url: './offscreen.html',
-    reasons: ['IFRAME_SCRIPTING'],
-    justification:
-      'Used for Hardware Wallet and Snaps scripts to communicate with the extension.',
-  });
+  try {
+    await chrome.offscreen.createDocument({
+      url: './offscreen.html',
+      reasons: ['IFRAME_SCRIPTING'],
+      justification:
+        'Used for Hardware Wallet and Snaps scripts to communicate with the extension.',
+    });
+  } catch (error) {
+    if (offscreenDocumentLoadedListener) {
+      chrome.runtime.onMessage.removeListener(offscreenDocumentLoadedListener);
+    }
+    if (
+      error?.message?.startsWith(
+        'Only a single offscreen document may be created',
+      )
+    ) {
+      console.debug('Offscreen document already exists; skipping creation');
+    } else {
+      // Report unrecongized errors without halting wallet initialization
+      // Failures to create the offscreen document does not compromise wallet data integrity or
+      // core functionality, it's just needed for specific features.
+      captureException(error);
+    }
+    return;
+  }
 
   // In case we are in a bad state where the offscreen document is not loading, timeout and let execution continue.
   const timeoutPromise = new Promise((resolve) => {