workaround for cores showing internal load errors with xml loader

if we pass the core's own error message over to the user without xml, the dialog they see is the regular "core accepted the rom + error message" one. but if the same happens for something loaded through xml, the dialog is instead "no core could load this + 2 copies of the same error/stack".

turns out there's a special case when MissingFirmwareException is thrown to avoid that second dialog. but internal errors are not MissingFirmwareException, so I added my own and a check for it.

unfortunately when running the debug build of hawk PLUS release build of dsda and causing such an internal error, there's still stack overflow after the throw...

Author: vadosnaprimer

src/BizHawk.Client.Common/RomLoader.cs

@@ -429,8 +429,11 @@ private IEmulator MakeCoreFromCoreInventory(CoreInventoryParameters cip, string
 				{
 					return core.Create(cip);
 				}
-				catch (Exception e) when (!_config.DontTryOtherCores
-					&& e is not (MissingFirmwareException or { InnerException: MissingFirmwareException }))
+				catch (Exception e) when (!_config.DontTryOtherCores && e is not (
+					MissingFirmwareException
+					or InternalErrorException
+					or { InnerException: MissingFirmwareException }
+				))
 				{
 					exceptions.Add(e);
 				}

src/BizHawk.Emulation.Common/EmulationExceptions.cs

@@ -41,4 +41,11 @@ public SavestateSizeMismatchException(string message)
 		{
 		}
 	}
+
+	public class InternalErrorException : Exception
+	{
+		public InternalErrorException(string message) : base(message)
+		{
+		}
+	}
 }

src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.cs

@@ -77,7 +77,7 @@ public MAME(CoreLoadParameters<object, MAMESyncSettings> lp)
 			if (_loadFailure.Length is not 0)
 			{
 				Dispose();
-				throw new Exception("\n\n" + _loadFailure);
+				throw new InternalErrorException("\n\n" + _loadFailure);
 			}
 
 			// concat all SHA1 hashes together (unprefixed), then hash that

src/BizHawk.Emulation.Cores/Computers/Doom/DSDA.cs

@@ -379,7 +379,7 @@ private static bool PlayerPresent(DoomSyncSettings syncSettings, int port) =>
 
 		private void ErrorCallback(string error)
 		{
-			throw new Exception($"\n\n{error}\n");
+			throw new InternalErrorException($"\n\n{error}\n");
 		}
 
 		/// <summary>