bugfix: draw edges after nodes they connect

The crash wasn't actually on the second node, it was just
indeterministic.

0028-A

@@ -5,6 +5,9 @@ A = function(preserve_screen_top_of_cursor_node)
 	for key,node in pairs(Nodes) do
 		node.id = key
 		compute_layout(node, node.x,node.y, Surface, preserve_screen_top_of_cursor_node)
+	end
+	-- draw edges after all nodes have been initialized
+	for key,node in pairs(Nodes) do
 		for _,d in ipairs(node.outgoing_edges) do
 			compute_layout_for_edge(key, d)
 		end