Rewards extension icon does not respond to clicks

[bsclifton]

Description

When using the browser, a LARGE number of notifications is shown:

However, clicking the icon does nothing (nothing logged to stdout, or background page, etc)

When inspecting using the task manager, a large % of CPU is being used:

Steps to Reproduce

Unknown - but @petemill and I both are experiencing this

Reproduces how often:

100% with my profile

Brave version (brave://version info)

Brave	0.67.2 Chromium: 74.0.3729.131 (Official Build) nightly(64-bit)
Revision	518a41c1fa7ce1c8bb5e22346e82e42b4d76a96f-refs/branch-heads/3729@{#954}
OS	Mac OS X

Version/Channel Information:

• Can you reproduce this issue with the current release? unknown
• Can you reproduce this issue with the beta channel? unknown
• Can you reproduce this issue with the dev channel? unknown
• Can you reproduce this issue with the nightly channel? Y

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? N
• Does the issue resolve itself when disabling Brave Rewards? N
• Is the issue reproducible on the latest version of Chrome? N/A

Miscellaneous Information:

[jsecretan]

Important to note in this is that it pegs CPU at a 100% when this happens, so actually much worse than it initially seemed.

[bsclifton]

Marked as QA/No because this might be tricky to test

However, @petemill and I both have profiles where this happens and have verified the fix. We can try to share steps to force this to happen (manually editing files) if needed