#625 Backup stops on file error

[emblendung]

On Debian 9 with JRE 1.8.0_231-b11, backup task stops when cannot read a file. Rather than stopping it should skip the file, log the issue, and continue.
The error message says: Error during storage of <filename> (no such file or directory).
Unfortunately, due to the issue, the software is unusable. This is why the issue whould be dealt with priority.</filename>