When selecting a light in the Radiant (builtin Windows-only level editor)
and pressing `j`, the light editor opened (as expected) but said that
no entity was selected.
That was because com_editorActive was false, most probably because of
e8a1eb8b Fix mouse remaining ungrabbed when running map from Radiant
which sets com_editorActive to false (via com->ActivateTool(false)) if
the Radiant window loses focus, which should be the case when opening
the light editor window.
`com_editors & EDITOR_RADIANT` is != 0 as long as the radiant is
running, no matter which window currently has focus, so it works better.
Editor also seems to start, didn't test much further.
Only tested 32bit Windows, I fear the editor code isn't 64bit clean..
I hope I haven't broken anything elsewhere..