Similar to commit 8b062418 (MetaType: Fix operator{+,-}(int)
with the type-erased const_iterators., 2013-09-11), explicitly
create a copy of the iterator and intialise it.
Change-Id: I8b9edef40ca00c826f72768cba4a0992e55371f8
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>