#306 IllegalArgumentException due to void type parameter

> Requesting Class<void> is in general a legitimate case, so I think this method should be able to handle it (also if we may not need it atm.). Shouldn't void methods be excluded much earlier in the matching routine?

I thought about this. You are probably right. Some observations:
1. If @TargetType is not involved, the mapping from 'x' to 'y' via 2 void methods (so x -- void - void -- y) is not resolved as a valid mapping (did not investigate why, but it was not sufficient to reproduce the problem).
2. The solution to get a `Class<void>` should never result into the exception.
3.  The solution to get a `Class<void>` should yield a valid class. Possibly just `Class` (without any parameters) right?

3. could be improved to my solution. 1. needs to be investigate a bit further. Shall we open another issue for that (as a reminder)?