Bugfix: Fix possible crash in the progress bar of check --read-data

We've fixed a possible crash while displaying the progress bar for the
check --read-data command. The crash occurred when the length of the
progress bar status exceeded the terminal width, which only happened for
very narrow terminal windows.

https://github.com/restic/restic/pull/2899
https://forum.restic.net/t/restic-rclone-pcloud-connection-issues/2963/15