Editing enum values used by Switch causes nullref

There are several issues in the area:

Steps to reproduce:

1. Create a new Behavior Graph.
2. Create a new enum in Blackboard.
3. Add a Switch node and assign that enum.
4. Connect a LogMessage node to one of the Switch port
5. Rename/Add/remove an enum member.
6. Focus editor after domain reload and interact with graph (move/select nodes, reconnect edges).

Actual results: 

• Rename/add enum member: repeated nullref spam originating from edge mapping rebuild (GraphView).
• Remove enum member: initial “Port UI missing for port …” then additional spam on further interaction.

Expected results:

• Graph detects enum mutation and safely reconciles ports/edges without console errors.

Reproducible with versions: 1.0.14

Not reproducible with versions:

• 1.0.12
• 1.0.13 also have nullref exception but reopening the graph fix the issue. Behavior got worse in 1.0.14.

Tested on (OS): WinEditor

Notes:

• Workaround: Detach enum from Switch, edit enum, reattach enum.