Handle 404 and 403 errors from uphold

[NejcZdovc]

Resolves brave/brave-browser#9653

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Android
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that these changes pass automated tests (unit, browser, security tests) on
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that all lint errors/warnings are resolved (npm run lint)
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone
• Public documentation has been updated as necessary. 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-issues-with-tracking-protection
  • https://github.com/brave/brave-browser/wiki/QA-Guide

Test Plan:

• enable rewards
• claim grant
• connect KYC wallet with some BAT in it
• close browser
• go to Preferences and change external_wallets->uphold->address to something random
• start browser
• go to rewards page
• make sure that wallet is disconnected and that you see grant balance

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

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.

[zenparsing]

Since balance is always valid, do we need the && balance check in the if below?

[NejcZdovc]

that was my mistake as balance can be null, so we should still have checks for it. Fixed

[NejcZdovc]

CI passed on everything except brave/brave-browser#9687

[LaurenWags]

Verified using

Brave | 1.10.56 Chromium: 81.0.4044.138 (Official Build) nightly (64-bit)
-- | --
Revision | 8c6c7ba89cc9453625af54f11fd83179e23450fa-refs/branch-heads/4044@{#999}
OS | macOS Version 10.14.6 (Build 18G3020)

• Verified test plan from description

Prior to changing the address field in Preferences file:

After changing the address field in Preferences file:

[ RESPONSE - OnFetchBalance ]
> time: 1589470441
> result: Failure
> http code: 404

Note - attempted to reconnect after completing the test plan, but was unsuccessful. Reviewed and discussed with @NejcZdovc - logged brave/brave-browser#9780.