Threads relating to deleted assistants are stuck in loading state with assistant name as "Tildy"

[sangee2004]

Electron build - 0bdee033a02

Steps to reproduce the problem:

1. Create an assistant.
2. Chat with the assistant and have some conversation.
3. Delete the assistant.

Notice that the threads relating to this assistant now shows up with assistant name as "Tildy" and is stuck in "loading" state near the chat message field.

[thedadams]

This is essentially a duplicate of #90 (although the outcome has changed since this issue was created).

We need to do something intelligent with threads where the assistant has been deleted.

[cjellick]

Im going to close this as a dupe of #90