Menu fixes
This is a variation of terminx/eduke32!74 (merged), aiming to take care of mods defining a part of the skill names as empty strings. It is not a 100% identical set of changes, but the ones present should make the code closer to what's currently in EDuke32.
As in the case of the EDuke32 MR, the Suburbs TC referenced there is also a good test case here.
For NetDuke32, I originally reproduced this in Speedtrax Racing. Since it was made to be run as a standalone game (requiring just executable files for DOS), I suggest to unpack into a separate directory and run NetDuke32 from there with the switch -usecwd. The game was designed for use without jumping or crouching, thus explaining the inclusion of a CFG file. I didn't see the same stated about strafing; Technically speaking, the included CFG lets you strafe with a mouse button.