Argument Exception thrown while playing ROM

[Game4all]

Recent work to improve emulator performance (namely #6) seems to have introduced a bug.

An exception will now throw while playing some ROMs such as Super Mario Bros Deluxe whereas it used to work correclty with an earlier emulator version.

Git bisect yields 912a7ee as the first bad commit.

The stack trace in question:

   at System.Buffer.BlockCopy(Array src, Int32 srcOffset, Array dst, Int32 dstOffset, Int32 count)
   at Emux.GameBoy.Cartridge.MemoryBankController5.ReadBytes(UInt16 address, Byte[] buffer, Int32 bufferOffset, Int32 length) 
   at Emux.GameBoy.Cartridge.EmulatedCartridge.ReadBytes(UInt16 address, Byte[] buffer, Int32 bufferOffset, Int32 length) 
   at Emux.GameBoy.Memory.GameBoyMemory.ReadBlock(UInt16 address, Byte[] buffer, Int32 offset, Int32 length)
   at Emux.GameBoy.Memory.DmaController.StartVramDmaTransfer() <------------------ Where the problem is
   at Emux.GameBoy.Memory.DmaController.WriteRegister(UInt16 address, Byte value)
   at Emux.GameBoy.Memory.GameBoyMemory.WriteByte(UInt16 address, Byte value)
   at Emux.GameBoy.Cpu.Z80OpCodes.<>c.<.cctor>b__3_220(GameBoy d, Z80Instruction i)
   at Emux.GameBoy.Cpu.Z80OpCode.<>c__DisplayClass9_0.<.ctor>b__0(GameBoy d, Z80Instruction i)
   at Emux.GameBoy.Cpu.Z80Instruction.Execute(GameBoy device)
   at Emux.GameBoy.Cpu.GameBoyCpu.PerformNextInstruction()
   at Emux.GameBoy.GameBoy.CpuLoop()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()