Catch TypeError in $lib.base64.decode() (SYN-7752)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.74%. Comparing base (e7cdbc4) to head (5578a50).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3827 +/- ## ========================================== - Coverage 96.81% 96.74% -0.08% ========================================== Files 241 241 Lines 52906 52906 ========================================== - Hits 51220 51182 -38 - Misses 1686 1724 +38 ``` | [Flag](https://app.codecov.io/gh/vertexproject/synapse/pull/3827/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vertexproject) | Coverage Δ | | |---|---|---| | [linux](https://app.codecov.io/gh/vertexproject/synapse/pull/3827/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vertexproject) | `96.74% <100.00%> (ø)` | | | [linux_replay](https://app.codecov.io/gh/vertexproject/synapse/pull/3827/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vertexproject) | `?` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vertexproject#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.