rewards widget "Ad earnings received" message missing BAT value in certain case

[LaurenWags]

Description

Found while testing #17483

"Ad earnings received" Rewards widget message doesn't display earned BAT value on upgrade profile.

Note - when an ad grant was issued to 1.33.x profile, the message displayed the BAT value appropriately.

Steps to Reproduce

1. Set up profile with 1.32.x, enable BR (staging env). Close UGP message on NTP widget.
2. Ask Chris to send you an ad grant.
3. Wait for Ad grant, see message on existing NTP widget.
4. Upgrade to 1.33.x.
5. Widget shows the appropriate message and but BAT value is 0.0.
6. Confirm clicking "Claim Earnings" opens the panel and shows the captcha.
7. Confirm able to claim the captcha.

Actual result:

Message shows 0.0 BAT:

Expected result:

message should show actual BAT value (12 in my example above).

Reproduces how often:

easily

Brave version (brave://version info)

1.33.94

Version/Channel Information:

• Can you reproduce this issue with the current release? n/a
• Can you reproduce this issue with the beta channel? yes
• Can you reproduce this issue with the nightly channel?

Other Additional Information:

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

Miscellaneous Information:

cc @Miyayes @zenparsing

[LaurenWags]

Verified using

Brave | 1.33.100 Chromium: 96.0.4664.55 (Official Build) (x86_64)
-- | --
Revision | 38cededc5d09b785d12203f1d3209aa6eb293e79-refs/branch-heads/4664@{#1090}
OS | macOS Version 11.6.1 (Build 20G224)

Verified STR from #19833 (comment)

1. Set up profile with 1.32.113, enable BR (staging env). Close UGP message on NTP widget.
2. Ask Chris to send you an ad grant.
3. Wait for Ad grant, see message on existing NTP widget.
4. Upgrade to 1.33.x.
5. Confirm widget does not show ad grant message.
6. Confirm panel and brave://rewards show ad grant is available for claim.
7. Confirm able to claim ad grant and balance increases as expected.

1.32.x NTP Widget	1.33.x NTP Widget	1.33.x brave://rewards	Claim Ad Grant	1.33.x NTP Widget after ad grant claim

Supplemental case:

1. Set up profile with 1.32.113, enable BR (staging env). Close UGP message on NTP widget.
2. Ask Chris to send you 2-3 ad grants.
3. Wait for Ad grant, see message on existing NTP widget.
4. Upgrade to 1.33.x.
5. Confirm widget does not show ad grant message for any of the ad grants.
6. Confirm panel and brave://rewards show ad grant is available for claim.
7. Confirm able to claim ad grants and balance increases as expected.

1.32.x NTP Widget	1.33.x NTP Widget	1.33.x Panel	1.33.x NTP Widget after ad grant claim