Support NOP opcode (w/ fix?)

[ZetaTwo]

When I tried to decompile a pyc with NOPs in it, I got the message "Unsupported opcode: NOP"

I tried to add the following to ASTree.cpp at line 779.

case Pyc::NOP:
            break;

Which seems to solve the problem since a NOP don't need any further processing, right?
I don't know the codebase enough to know if I need to do other changes elsewhere which is why I'm posting this as an issue instead of a PR.