Most leaks fixed by adding deallocation in the early exit branch,
some fixed by rearranging code to put the early exit before the
allocation. Also removed some unnecessary checks for null before
using delete.

Presumably none of these branches are covered by tests,
or valgrind would find the leaks.  cppcheck found them though!

Change-Id: Iecad8ca988abc560939d46bf0a5a9e7e5a1511a5