In my opinion there is nothing bad with it.
Generally you would want to maintain a pointer to the singleton, not to
some object that it contains. By keeping a pointer to the object it
contains you are adding a harder dependency and a requirement that that
object doesn't change or changes in some defined way. If you have defined
and documented that then it should be ok, but, usually the singleton should
be able to destroy that object and create a new one as required so you may
want to rethink keeping a reference to it.
Keeping a reference to the singleton itself is fine because that will
never be destroyed.
Properties will point to the same address as property in Singleton
and after non-singleton class will be destroyed also properties that
where pointing to singleton so Reference Count = Refrence count - 1.