Restored analyzers with missing files end up in queue

[ybnd]

Analyzers appear in queue w/ infinite loading animation

TODO:

• If the analyzer can't be launched, don't add it to the queue
• In this case VideoAnalyzer.can_launch should log warnings about the specific files that are missing, but it doesn't. Why?
• BaseAnalyzer.launch should log a more comprehensive warning
• A notification should be pushed to the frontend to inform the user that an analyzer was skipped when restoring the state & why