Thanks, got it.
It's in message list layout code, and it's crashing when breaking two-line message content preview into lines.
Please try this as a workaround:
Start the app without opening a message list, then app settings -> message list -> change "with preview" to 1 line.
Do you have recent messages (that would be displayed in this folder / message list) that have right to left characters (Arabic, Hebrew, Thai, etc.)?