Crash when trying to open brave://sync in Guest Window

[btlechowski]

Follow up from #2852

Steps to Reproduce

1. Open Guest Window
2. Open brave://sync

Actual result:

Crash

Expected result:

No crash

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Brave	0.62.8 Chromium: 73.0.3683.39 (Official Build) dev (64-bit)
Revision	cc53b0e12fcaf42e4bab8d6c23bd4fb7aae99f6c-refs/branch-heads/3683@{#413}
OS	Windows 7 Service Pack 1 Build 7601.24312

Brave	0.61.39 Chromium: 73.0.3683.39 (Official Build) beta (64-bit)
Revision	cc53b0e12fcaf42e4bab8d6c23bd4fb7aae99f6c-refs/branch-heads/3683@{#413}
OS	Windows 7 Service Pack 1 Build 7601.24312

Related issues: #3003.

@simonhong I have not seen this issue reported for Guest Window.

cc @brave/legacy_qa

[simonhong]

@btlechowski This was also fixed by brave/brave-core#1704.
That PR handles crash on Tor and Guest both.

[kjozwiak]

@btlechowski mind taking a look and seeing if it's an issue on 0.63.x. Might have to build from source as we don't have nightly builds yet. If you would like, I can check on macOS as I have a recent build already 👍

[btlechowski]

Based on #3522 (comment) the issue was fixed in brave/brave-core#1704

[btlechowski]

Verification passed on

Brave	0.63.4 Chromium: 73.0.3683.67 (Official Build) dev (64-bit)
Revision	a83fd4f3207ae83412d329a9ca1239dd1e068345-refs/branch-heads/3683@{#760}
OS	Windows 7 Service Pack 1 Build 7601.24312

Used test plan from the description

Verification passed on

Brave	0.63.7 Chromium: 73.0.3683.75 (Official Build) dev (64-bit)
Revision	909ee014fcea6828f9a610e6716145bc0b3ebf4a-refs/branch-heads/3683@{#803}
OS	Linux

• Verified the STR mentioned in the description
  

Verification PASSED on macOS 10.14.3 x64 using the following build:

Brave	0.63.9 Chromium: 73.0.3683.75 (Official Build) dev (64-bit)
Revision	909ee014fcea6828f9a610e6716145bc0b3ebf4a-refs/branch-heads/3683@{#803}
OS	Mac OS X

• ensured that both chrome://sync and brave://sync didn't cause any crashes