BizHawk crashes during saving when save files are in use by other processes (Dropbox)

Summary

When BizHawk attempts to save to a file that is being accessed by Dropbox, an error dialog will pop up, then BizHawk will crash entirely.

I'm on Windows, using a personally modified version of BizHawk forked from late 2.9 cc0f1417f1fa64fa267896a45c55417f707428dc, with some minor changes to file extensions - nothing that would affect this.

Ideally this should fail and try again later, rather than crash the entire program.

I've tried to find similar issues and can't find any, apologies if I missed any. I also apologise if this has been fixed with 2.10.

Repro

1. Run BizHawk while its save directory is pointed at a directory managed by Dropbox.
2. Play a game, optionally with autosaving enabled.
3. Wait for a clash between BizHawk autosaving and Dropbox syncing.

Output

System.IO.IOException: The process cannot access the file 'C:\Users\Ladybunne\Dropbox\Media\Games\Emulation\SaveRAM\GBA\Yu-Gi-Oh! - Ultimate Masters - World Championship Tournament 2006 (USA) (En,Ja,Fr,De,Es,It).Autosave.srm.bak' because it is being used by another process.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileInfo.Delete()
   at BizHawk.Client.EmuHawk.MainForm.FlushSaveRAM(Boolean autosave) in C:\Users\Ladybunne\repos\BizHawk\src\BizHawk.Client.EmuHawk\MainForm.cs:line 2002
   at BizHawk.Client.EmuHawk.MainForm.StepRunLoop_Core(Boolean force) in C:\Users\Ladybunne\repos\BizHawk\src\BizHawk.Client.EmuHawk\MainForm.cs:line 3051
   at BizHawk.Client.EmuHawk.MainForm.ProgramRunLoop() in C:\Users\Ladybunne\repos\BizHawk\src\BizHawk.Client.EmuHawk\MainForm.cs:line 897
   at BizHawk.Client.EmuHawk.Program.SubMain(String[] args) in C:\Users\Ladybunne\repos\BizHawk\src\BizHawk.Client.EmuHawk\Program.cs:line 352

Host env.

• Modified BizHawk dev build from late 2.9 cc0f1417f1fa64fa267896a45c55417f707428dc (see here: https://github.com/ladybunne/BizHawk/tree/srm-crimes)

Start in src/BizHawk.Client.EmuHawk/MainForm.cs at MainForm.FlushSaveRAM, identified in the stack trace around line 2002, and follow its call from the save loop. Reproduce an autosave while Dropbox holds the .bak file; done means the lock no longer crashes BizHawk and the save failure is handled as described.