[Gtkradiant] Entity of class misc_model without a model cannot be directly selected

[Obsidian]

Originally reported on mfn's experimental branch, but I can confirm
bug is still active in latest 1.6 build. I suggest adopting behaviour
from 1.5.



https://github.com/mfn/GtkRadiant/issues#issue/6

Requires a selection operation like "select inside", shift click on
that entity does not work (Reported by Rambetter).

mfn January 02, 2010:
Another work-around: activate "Show entities as -> bounding box",
selecting now works, too.

Hipshot January 08, 2010:
I guess this might be a bit on the advanced side, but you might wanna
have it so if radiant can't find a model, it uses a default one, like
a debug thing from the PK3 or something micro that can be shipped with
the editor, like an "X (cross)" that is the icon for missing model or
similar.