Bump version
Fix NullPointerException in PageActivity

If next page is bonus, but not the last, but still in the last group, we
got to a NullPointerException.
Update grammar version
Update changelog
Merge branch 'hotfix/0.17.1'
Merge tag '0.17.1' into develop

* Bug fixes
  * Fix NullPointerException in PageActivity if nextPage is bonus with no following pageGroup