Give a more specific message when a category tries to update itself after the database has been closed when stopping the server

[CC007]

See logs.

TLDR: when a category is being updated, but the server is stopped at the same time, the database will be closed and the following error will be thrown:

[11:59:46] [Craft Scheduler Thread - 11 - HeadsPluginAPI/WARN]: [HeadsPluginAPI] Plugin HeadsPluginAPI v3.2.0 generated an exception while executing task 39 
    org.apache.openjpa.persistence.PersistenceException: connection exception: closed { <sql statement> } 
    <stacktrace>

It would be nice if this exception was caught and only a warning was logged regarding being unable to finish updating the categories.