[Fixed for V0.42] Crash when leaving replace spell dialog

[R.K.]

Clicking either "cancel" or "OK" in the dialog for replacing builtin spells results in a divide by zero:

Error:
an integer divide by zero exception.

Stack Dump:
utilMemory.utilFreeCheckBlock(pointer 0x00000000);
utilMemory.utilFree(pointer 0x028014B0, char 14);
RTCEditDlgNewSpells.OnButtonAddEx();
RTCEditView.OnResourceSpells();
RTCEditApp.WinMain();

[George Gilbert]

Fixed for V0.42