This fixes a potential regression introduced in
34b8e38ef25242a4992f61c8676569a8dcffc7f7 When that commit was
done some instanceof checks were removed.
The result of removing the instanceof checks had the side effect
of removing the implicit null check that instanceof essentially
does.

This change restores the null checks for all the instanceofs that
were removed in 34b8e38ef25242a4992f61c8676569a8dcffc7f7