Replace !! operators with proper null checks to prevent
NullPointerExceptions when encodedFormat or muxerContext are null.
This can happen if createNextMuxer is called before
onOutputFormatChanged sets the format.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Prevents crash when an exception with null message is caught and rejected
through the React Native bridge.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>