Steps to replicate the issue:
<pgn> [Event "Chess Game"] [Result "1-0"] 1. e4 {this comment spans two lines} e5 </pgn>
What happens?:
ChessBrowser throws an exception. I've tracked it down to assertValidPGN().
What should have happened instead?:
A board should have been created or a more helpful error message should have been shown.
Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):
Other information (browser name/version, screenshots, etc.):