Fix #18918 - Null deref in BRAVE_ICON_LABEL_BUBBLE_VIEW_GET_HIGHLIGHT_PATH

[jumde]

Resolves brave/brave-browser#18918

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested 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:

1. Enable media router in brave://settings/extensions
2. Enable all cast flags in brave://cast
3. Navigate to https://jumde.github.io/test/cast.html and click cast
4. Should not crash

[petemill]

Out of interest are you aware of which icon label bubble view is being made in this scenario where there is no layoutprovider? I presume it's related to casting and it gets created when

request = new PresentationRequest([location]);
   request.start().then(
   connection=>{
   console.log(2);
   }

is run

edit: I guess it's this

[mkarolin]

chromium_src++

[jumde]

Out of interest are you aware of which icon label bubble view is being made in this scenario where there is no layoutprovider? I presume it's related to casting and it gets created when

request = new PresentationRequest([location]);
   request.start().then(
   connection=>{
   console.log(2);
   }

is run

edit: I guess it's this

right

[nullhook]

LGTM

[petemill]

++

[petemill]

++