esx: Fix dynamic deep copy

esx: Fix dynamic deep copy

The static deep copy allocates storage for the copy. The dynamic
version injected the dynamic dispatch after the allocation. This
triggered the invalid argument check in the dynamically dispatched
deep copy call. The deep copy function expects its dest parameter
to be a pointer to a NULL-pointer. This expectation wasn't met due
to the dispatching deep copy doing the allocation before the call.

Fix this by dynamically dispatching to the correct type before the
allocation.