[Graph] Workspace breaks with no user message when index pattern was removed

[mbondyra]

Kibana version:
master

1. Add any index pattern, any sample data is ok
2. create a graph workspace on this index pattern
3. remove index pattern in stack management section
4. come back to the vis: it just doesn't load. Console log throws an error.

Additional details: this doesn't work also when the index pattern is in 'conflict' state - when working on it, make sure to go through the test cases from the description of this PR and check it works for it too. Please use your own exported saved object as the one there might be outdated.

Expected behavior would be to at least show a notification why it doesn't load.

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[kertal]

thx @mbondyra , agreed, it should not fail silently

[dimaanj]

It's known historical one (before deangularization), which was already issued here. Seems like we can close the current one, isn't it?

[mbondyra]

👌🏼 Sounds good @dmitriynj , closing.