Sketchbook setting lost when Linux mount fails

I have my Sketchbook folder on a NAS and my Linux computers don't always mount the folder as they shall when it starts. If I then launch Arduino IDE it tells me that the Sketchbook is lost and changes the setting for the Sketchbook folder. I think this behavior is wrong, why not just tell me the Sketchbook folder is missing and let the setting be? I can then correct the mount issue without going through the trouble of changing the settings.

Start by tracing the Arduino IDE 1.x startup handling for the Sketchbook setting when its Linux-mounted folder is unavailable. Reproduce the missing-mount case and verify that the configured folder is preserved while the user is informed that it is missing.

Written by the indexing model from the issue text.