Notifications cannot be dismissed if currentNotification is not in list

[bsclifton]

Description

There may be situations (legacy, debugging, etc) where a notification was shown and is somehow stored as state.currentNotification in the Rewards extension.

Steps to Reproduce

1. Ask @bsclifton for profile if needed
2. Put profile in place
3. See 33 notification count on Rewards extension
4. Click rewards extension
5. No notification shows up

Actual result:

No notification shown in popup

Expected result:

Notification should be shown in the popup

[btlechowski]

Asked @bsclifton for the profile. Added QA/Blocked.

[btlechowski]

Verification passed on

Brave	0.71.93 Chromium: 77.0.3865.90 (Official Build) dev (64-bit)
Revision	58c425ba843df2918d9d4b409331972646c393dd-refs/branch-heads/3865@{#830}
OS	Ubuntu 18.04 LTS

Verified test plan from the description

Verified that notification is shown

Verified that user can click OK to dismiss the notification
Verified that user can click x to dismiss the notification
Verified that number of notifications is decreasing when dismissed

Verified passed with

Brave	0.71.103 Chromium: 78.0.3904.70 (Official Build) beta (64-bit)
Revision	edb9c9f3de0247fd912a77b7f6cae7447f6d3ad5-refs/branch-heads/3904@{#800}
OS	macOS Version 10.13.6 (Build 17G5019)

• Verified test plan from description
• Confirmed user can click OK to dismiss notification (when OK is available)
• Confirmed user can click x to dismiss notification
• Confirmed that the number of notifications decreases with each notification dismissed

Verification passed on

Brave	0.71.104 Chromium: 78.0.3904.70 (Official Build) beta (64-bit)
Revision	edb9c9f3de0247fd912a77b7f6cae7447f6d3ad5-refs/branch-heads/3904@{#800}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified test plan from the description
• Confirmed user can click OK to dismiss notification (when OK is available)
• Confirmed user can click x to dismiss the notification
• Confirmed that the number of notifications decreases with each notification dismissed