Missleading missing opcode error message.

[MiranDMC]

Popup error message informs about invalid use of opcode, meanwhile text at the bottom of the windows reports that the opcode is not known at all (which was actual cause).

Generally many message boxes lack information about opcode number and its name, making it difficult to research.
Also, It would be nice to have another webpage link in the message leading to SBL about the miss used opcode.