Non-graceful exit under GNOME Wayland

Opening EmuHawk and immediately closing it through any means except ^C results in:

System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
  at System.Collections.Generic.Dictionary`2+ValueCollection+Enumerator[TKey,TValue].MoveNext () [0x00016] in <12b418a7818c4ca0893feeaaf67f1e7f>:0
  at BizHawk.Bizware.Input.SDL2InputAdapter.ProcessHostGamepads (System.Action`3[T1,T2,T3] handleButton, System.Action`2[T1,T2] handleAxis) [0x00132] in <ce180a9d7f004a49ac5715aafc01c18b>:0
  at BizHawk.Client.EmuHawk.Input.UpdateThreadProc () [0x000c3] in <e894146d24774d20b93bd742debe8259>:0
  at System.Threading.ThreadHelper.ThreadStart_Context (System.Object state) [0x00017] in <12b418a7818c4ca0893feeaaf67f1e7f>:0 
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x0008d] in <12b418a7818c4ca0893feeaaf67f1e7f>:0 
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00000] in <12b418a7818c4ca0893feeaaf67f1e7f>:0 
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state) [0x00031] in <12b418a7818c4ca0893feeaaf67f1e7f>:0 
  at System.Threading.ThreadHelper.ThreadStart () [0x0000b] in <12b418a7818c4ca0893feeaaf67f1e7f>:0 

I believe this goes back to 2.10 or 2.9.1.

Start at BizHawk.Bizware.Input.SDL2InputAdapter.ProcessHostGamepads and follow its callers into BizHawk.Client.EmuHawk.Input.UpdateThreadProc. Reproduce by opening EmuHawk under GNOME Wayland and closing it without Ctrl+C, then investigate the reported collection-modification exception. Done means the application exits without this exception through the reported close paths.