fix: issue where user rejected request errors are not correctly handled in either wallet_switchEthereumChain nor wallet_addEthereumChain calls

[adonesky1]

Description

A bug was introduced in #24415, where user rejected request errors are not correctly handled in either wallet_switchEthereumChain nor wallet_addEthereumChain calls.

Related issues

Fixes: Regression in API error handling found on a local run of the new API testing tool, will link report when available.

Manual testing steps

wallet_addEthereumChain

1. Go to https://docs.metamask.io/wallet/reference/wallet_addethereumchain/
2. Submit the prepopulated wallet_addEthereumChain request
3. Confirm the request to add Gnosis Chain
4. But click "Cancel" on the second request to switch to the newly added chain
5. You should see null as the response

wallet_switchEthereumChain

1. Make sure the wallet is on a chain other than gnosis
2. Go to https://docs.metamask.io/wallet/reference/wallet_switchethereumchain/
3. Submit the prepopulated switchEthereumChain request (for chainId: 0x64)
4. Click cancel on the request to switch to gnosis chain
5. you should see:

{
  "code": 4001,
  "message": "User rejected the request.",
  "stack": "{\n  \"code\": 4001,\n  \"message\": \"User rejected the request.\",\n  \"stack\": \"Error: User rejected the request.\\n  
 }

in the response

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). 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.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 65.61%. Comparing base (e407384) to head (6dd5a0c).

Files	Patch %	Lines
...method-middleware/handlers/ethereum-chain-utils.js	50.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #25269      +/-   ##
===========================================
- Coverage    65.62%   65.61%   -0.01%     
===========================================
  Files         1372     1372              
  Lines        54512    54519       +7     
  Branches     14281    14282       +1     
===========================================
+ Hits         35769    35770       +1     
- Misses       18743    18749       +6     

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[metamaskbot]

Builds ready [6dd5a0c]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (MMI): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
  • content-script: 0
  • offscreen: 0
  • ui: 0, 1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (130 ± 156 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	72	110	88	11	5
		domContentLoaded	9	21	11	2	1
		load	42	1545	130	325	156
		domInteractive	9	21	11	2	1