multi: add models.Node V1 constructor

Add a version field to models.Node and a V1 constructor for it.

graph/db/notifications.go

@@ -391,9 +391,11 @@ func (c *ChannelGraph) addToTopologyChange(update *TopologyChange,
 		nodeUpdate := &NetworkNodeUpdate{
 			Addresses:   m.Addresses,
 			IdentityKey: pubKey,
-			Alias:       m.Alias,
-			Color:       EncodeHexColor(m.Color),
-			Features:    m.Features.Clone(),
+			Alias:       m.Alias.UnwrapOr(""),
+			Color: EncodeHexColor(
+				m.Color.UnwrapOr(color.RGBA{}),
+			),
+			Features: m.Features.Clone(),
 		}
 
 		update.NodeUpdates = append(update.NodeUpdates, nodeUpdate)