Toggling deep-sky objects should toggle custom catalogs too

Most custom catalogs are catalogs of deep-sky objects. There could be
exceptions, of course, but it is much less likely. Thus, when toggling
deep-sky objects, most users might expect to turn off rendering of
custom catalog objects too and not just NGC/IC/M.

This change produces the behavior. A quick check for possible bugs
introduced in the form of crashes when searching for custom catalog
objects after turning off theitr display did not reveal any.