Comment # 1 on bug 1173550 from Michael Andres

There seem to be history files with embedded NUL charactes which break the
parser. Workaround, in case your file is corrupted similar to the reported
ones:

  Backup: 
  cp /var/log/zypp/history /var/log/zypp/history.orig

  Remove embedded zeros:
  cat /var/log/zypp/history.orig | tr -d '\000' >/var/log/zypp/history

*** This bug has been marked as a duplicate of bug 1170801 ***