Fix issue of memory leaking for coord objects. When coord.cc try to release memory of coords of a subtree, a typo make the code always free root coord of the subtree. It causes a leaking.

<project>
	<scene src='list.mbsvg' />
	<source src='main.c'/>
	<source src='%n.c'/>
	<source src='%n.h'/>
	<source src='Makefile'/>
</project>