libcnary: Fix memleak in node_debug()

An iter was created but never destroyed.
diff --git a/libcnary/node.c b/libcnary/node.c
index 6026925..3bd6975 100644
--- a/libcnary/node.c
+++ b/libcnary/node.c
@@ -142,6 +142,7 @@
 		for(current = iter->begin; current != NULL; current = iter->next(iter)) {
 			node_debug(current);
 		}
+		node_iterator_destroy(iter);
 	}
 
 }