Check failure while importing from welcome page

[simonhong]

Description

Crashed with master build (Version 1.8.32 Chromium: 81.0.4044.69 (Developer Build) (64-bit))

[47456:47456:0323/135125.549138:FATAL:import_data_handler.cc(116)] Check failed: args->GetDictionary(1, &types). 
#0 0x7f2dfa3f882f base::debug::CollectStackTrace()
#1 0x7f2dfa11444d base::debug::StackTrace::StackTrace()
#2 0x7f2dfa114408 base::debug::StackTrace::StackTrace()
#3 0x7f2dfa15a21d logging::LogMessage::~LogMessage()
#4 0x56514c25099b settings::ImportDataHandler::HandleImportData()
#5 0x56514c252bdb base::internal::FunctorTraits<>::Invoke<>()
#6 0x56514c252ac6 base::internal::InvokeHelper<>::MakeItSo<>()

Test plan / Steps to reproduce

1. Launch browser and load brave://welcome
2. Try to import from any profile
3. Importing should be done w/o crash

[LaurenWags]

Verified passed with

Brave	1.8.71 Chromium: 81.0.4044.92 (Official Build) dev (64-bit)
Revision	e98e6f21168a55e7ba57202f56323911cd9d31d1-refs/branch-heads/4044@{#883}
OS	macOS Version 10.14.6 (Build 18G3020)

• Verified test plan from description
• Confirmed history and bookmarks imported from Firefox using brave://welcome (note, encountered logged issue Passwords, Search Engine, and Autofill are not imported from Firefox #2198)
• Confirmed history, bookmarks, and passwords were imported from Chrome using brave://welcome.
• Confirmed no crashes observed when importing from brave://welcome

Verification passed on

Brave	1.8.72 Chromium: 81.0.4044.92 (Official Build) dev (64-bit)
Revision	e98e6f21168a55e7ba57202f56323911cd9d31d1-refs/branch-heads/4044@{#883}
OS	Ubuntu 18.04 LTS

• Verified test plan from description
• Verified history and bookmarks imported from Firefox using brave://welcome
• Verified history, bookmarks, and passwords were imported from Chrome using brave://welcome.

Verification passed on

Brave	1.8.77 Chromium: 81.0.4044.92 (Official Build) dev (64-bit)
Revision	e98e6f21168a55e7ba57202f56323911cd9d31d1-refs/branch-heads/4044@{#883}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified test plan from the description
• Verified history and bookmarks imported from Firefox using brave://welcome
• Verified history, bookmarks, and passwords were imported from Chrome using brave://welcome.

Verification passed on

Brave	1.8.77 Chromium: 81.0.4044.92 (Official Build) dev (64-bit)
Revision	e98e6f21168a55e7ba57202f56323911cd9d31d1-refs/branch-heads/4044@{#883}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified test plan from the description
• Verified history and bookmarks imported from Firefox using brave://welcome
• Verified history, bookmarks, and passwords were imported from Chrome using brave://welcome.

• Encountered Saved passwords not imported from chrome browser to brave #9269