Default Onslaught control point names to "<NO NAME>"

Fixes #2265 (closed).

This will make Onslaught control point names (message) in messages about destroying or capturing control points fall back to “<NO NAME>” is none is set. The idea is to force map makers to always set a name.

Current behaviour: By capturing a control point, a message like “Player captured <NAME> control point” appears. If the control point has a name, then “<NAME>” is replaced by a name. BUT! If the control point has NO name, then “<NAME>” is replaced by “a”. This creates “Player captured a control point”. This is a hacky bacause it screws up translations. In translations, the grammar of a sentence can vary wildly if you use an indefinite article instead of a name in a sentence. And it can just lead to very confusing messages.

How this MR works:

The “a” is replaced by “<NO NAME>”. That's it!