Add a check to an if-statement in CwCheat.cpp in function hleCheat.

Check if cheatEngine isn't null. Considering how the if-statement below it has this check, it should be placed in this one as well.
Simplify the previous commit's check a little bit.
Merge pull request #2435 from lioncash/master

Add an extra null check to an if statement in CwCheat's function hleCheat.