[FIX] vm not found issue when calling vmonkey with -e argument

[whikernel]

Hi !

Calling vmonkey with the -e argument to evaluate and deobfuscate results as followed vmonkey -e file.virus results in NameError: global name 'vm' is not defined.

Line 1652 of file vmonkey.py is making reference to vm without initializing it. This should correct it.