Case 1: node is root

color node as black it adds a black node on every path so we do nothing else

Property definitions

trees $ RBTreeMap :: insert_fixup_case1
	# Case 1: node is root
	# color node as black
	# it adds a black node on every path so we do nothing else
	private fun insert_fixup_case1(node: N) do
		if node.parent == null then
			node.is_red = false
		else
			insert_fixup_case2(node)
		end
	end
lib/trees/rbtree.nit:60,2--69,4