Avoid using erase()d iterator

After calling erase(it), 'it' is no longer valid and should not be
used as it was in the 'it++' of the 'for' loop.  We change to
update 'it' to the result of erase(), and only perform 'it++' if
we're not erasing it.

Test: TreeHugger
Change-Id: If7889fdca76a6883aeb4341be1a6fff466585e29