Brave crashes when visiting brave://settings when Sync disabled via brave://flags

[specter78]

Test plan

See brave/brave-core#15031

Description

Brave v1.43.88 crashes when Brave Sync V2 flag is disabled.

On windows - it crashes on launch

On macOS- it crashes on opening preferences

[rebron]

@specter78 Can you go into brave://crashes send the report and post the crash id in the thread if you get a chance.

[MadhaviSeelam]

Reproduced this issue in Win 11 x64

Brave | 1.43.85 Chromium: 105.0.5195.68 (Official Build) (64-bit)
-- | --
Revision | ad13e82529051bac6a0e65f455e6d7a1e5fd7938-refs/branch-heads/5195@{#903}
OS | Windows 11 Version 21H2 (Build 22000.856)

Crash Report ID: | a72d0300-74c0-c508-0000-000000000000

• install 1.43.88
• open brave://flags and disable sync v2 and relaunch the browser
• open brave://settings/ in a new tab

[bsclifton]

Also crashes on NTP when turning off brave://flags/#brave-news (as of 1.43)

• see https://brave.sp.backtrace.io/p/brave/debug?time=all&filters=(_deleted%3D0%2C_rxid%3Dff480300-74c0-c508-0000-000000000000)&fingerprint=f474f822724e029c733f764d14d6a3689e488010dfd3bbe6599865d124fd36ef&debug=(%223a3b954%22,0,0)
• see https://brave.sp.backtrace.io/p/brave/debug?time=all&filters=(_rxid%3Da12a0300-74c0-c508-0000-000000000000)&fingerprint=525f2d1423d8fb5228714c95f0affb11a3cdfd32f5e401c931b4fb4be239ec34&debug=(%223a39b14%22,0,7)

We should probably remove these two flags because they've outlived their use. We can remove the feature flag level checks too. There is a specific preference now for News enabled

[bsclifton]

Narrowed this down - this first appeared in 1.43.84 (1.43.83 was fine)

@mkarolin this may be related to the l10n updates - I'm not sure if it'll crash if a string is missing? I might need help narrowing it down.

Here's a quick link to the commit log for 1.43.84 to help see what commits were added:
https://github.com/brave/brave-core/commits/40863c335718591dcccc3537d04c273425fc3677

[kjozwiak]

The above requires 1.43.92 or higher for 1.43.x verification 👍

[GeetaSarvadnya]

Verification PASSED on

Brave | 1.43.92 Chromium: 105.0.5195.102 (Official Build) (64-bit)
-- | --
Revision | 4c16f5ffcc2da70ee2600d5db77bed423ac03a5a-refs/branch-heads/5195_55@{#4}
OS | Windows 10 Version 21H2 (Build 19044.1889)

Verified the test plan from brave/brave-core#15031
Reproduced the issue in 1.43.88
Confirmed that there is no crash when brave://settings opened once brave://flags/#brave-sync-v2 has been disabled in 1.43.92