fix: correct error type in WmctrlExecutor::executable?

[pluiedev]

Not sure if this needs a test case — either way I don't really know how to write one 😅

Fixes #13

[iberianpig]

Thank you. The constant missing error will be fixable with this PR.

However, we got my new task that needs to be fixed.

• It seems that it was not compatible with Fusuma 3, tests was failing
• I found a commit from a previous refactoring of the exception class.
  • f82644420cd78826a48dbe18678de
  • This refactoring is still not sufficient and the exception class must be wrapped on the Executor side and resubmitted as InvalidOptions.

I merge this PR, but the release will likely follow in order to proceed with the above tasks.