@Idolse. Thanks for reporting the issue. There are two things happening here - the first is a bug in the Generate Cover plugin which I have posted a new version to fix.
The second is as you say the plugin updater not more gracefully handling the problem of a plugin failing to load. I have added some logic into Plugin Updater to display a more user friendly dialog and uninstall the plugin in this situation. The error details are in the details portion and the user is asked to post in the relevant forum thread. I will release this update to Plugin Updater shortly.
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