ListBox doesn't get re-updated when re-connected

[sofian]

To reproduce:

• Put two different effects with EnumType inputs (eg. AlphaMix and VideoMix)
• Connect a ListBox to the effect A: its name/values are populated with effect A types
• Connect the ListBox to effect B: its names/values stay the same (because the are still connected to both: makes sense)
• Disconnect line to effect A: ListBox stays the same (whereas it should IMHO take the values of effect B)

Notice that it works properly if you disconnect the line to effect A before connecting to effect B. But I believe it is nonetheless a bug (even if minor).