Error when creating any NDS cheats

[webbedspace]

An error is preventing me from creating any Nintendo DS cheats.

Repro

1. Load Nintendo DS rom
2. open Cheats
3. Add a name to the blank cheat box, leaving Address and Value as is, and press Add

Output

System.NullReferenceException: Object reference not set to an instance of an object.
   at BizHawk.Client.EmuHawk.CheatEdit.GetCheat()
   at BizHawk.Client.EmuHawk.Cheats.AddCheat()
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Host env.

BizHawk dev build at b11bb4f; Win10;

[YoshiRulz]

Did this work in 2.8? And is it also broken with other cores? Based on the stacktrace I'd expect it to be.

[webbedspace]

No, doesn't work in 2.8.

[webbedspace]

OK, the cheat entry works with at least the SNES cores, so I believe it's NDS specific.

[YoshiRulz]

Invariant broken here @CasualPokePlayer. (In your defence, it wasn't documented that MainMemory/SystemBus must be in the collection.)

BizHawk/src/BizHawk.Emulation.Cores/Consoles/Nintendo/NDS/MelonDS.cs

Line 199 in 0b7960f

((MemoryDomainList)this.AsMemoryDomains()).SystemBus = new NDSSystemBus(this.AsMemoryDomains()["ARM9 System Bus"], this.AsMemoryDomains()["ARM7 System Bus"]);

[CasualPokePlayer]

I believe this was a specific hack intended to make the debugger happy and be able to switch between ARM7 and ARM9 System Buses depending on current CPU selected for the disassembler iirc?