If a value is assigned but never used it is an expensive

If a value is assigned but never used it is an expensive
memory operation that is never used. These changes remove
those assignments.

Note the dynamic_cast instead of the static_cast. Since
the cast is an up cast to the derived class, a dynamic_cast
is more appropriate. But since dynamic_cast can return zero
a pointer check is put in as well.

Signed-off-by: Erik Hovland <erik@hovland.org>