added op as a class variable. Its set in runFunction but not initialized by the class. There is a race triggered by some binaries (have the md5s) when emulating certain paths functions relying on op existing specifically getRegister in Amd64WorkspaceEmulator check for the variable before its set by runFunction
added check on the class variable op in base class WorkspaceEmulator to make sure its not None before continuing
Merge pull request #21 from vivisect/rp_amd64_fixes

Rp amd64 fixes