Fix crash with popup windows requesting Ethereum permission

[bbondy]

Resolves brave/brave-browser#19566

I wasn't able to get a test case working quickly but I posted this issue to look at it again. I just want to get the fix in and uplifted for the next hotfix first. brave/brave-browser#19567

Looks like this:

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have [requested]
  (https://github.com/brave/security/issues/new/choose) one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally: npm run test -- brave_browser_tests, npm run test -- brave_unit_tests, npm run lint, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[bridiver]

Deps ok

[srirambv]

Verification passed on

Brave	1.34.28 Chromium: 96.0.4664.45 (Official Build) nightly (x86_64 translated)
Revision:	76e4c1bb2ab4671b8beba3444e61c0f17584b2fc-refs/branch-heads/4664@{#947}
OS	macOS Version 12.0.1 (Build 21A559)

• Verified test plan from Fix crash when permission requests for Ethereum are from a popup window brave-browser#19566
• Verified connect popup is shown correctly and opens panel to connect
• Encountered the connect wallet failure due to webcompat bug mentioned in Fix crash when permission requests for Ethereum are from a popup window brave-browser#19566 (comment)

19566.mov