Brave crashes when Brave payment is disabled and enabled frequently

[srirambv]

Test plan

#7036 (comment)

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• Did you search for similar issues before submitting this one?
  Yes

• Describe the issue you encountered:
  Brave crashes when Brave payment is disabled and enabled frequently

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Windows 10 x64

• Brave Version (revision SHA):
  Brave 0.13.2
  rev ce14f5d

• Steps to reproduce:

  1. Enable Brave payments and wait till the wallet is created
  2. Disable payments and enable it immediately
  3. Repeat it for 4-5 times, brave crashes

• Actual result:
  Brave crashes after disabling/enabling payments in quick succession

• Expected result:
  Should not crash

• Will the steps above reproduce in a fresh profile? If not what other info can be added?
  Yes

• Is this an issue in the currently released version?
  Yes same issue on 0.13.1

• Can this issue be consistently reproduced?
  Yes

• Extra QA steps:
  1.
  2.
  3.

• Screenshot if needed:
  

• Any related issues:
  cc: @mrose17