Volker Enderlein authored Sep 30, 2019 and Paul Lemire committed Oct 01, 2019

- Fixed Ritter algorithm implementation
- Added notation of invalid bounding sphere (radius == -1.0)
- Handle merging of invalid bounding sphere with valid ones
- Added test cases and adjusted tests boundingsphere and
  proximityfilter
- This is necessary to ensure the correct working for viewAll and
  viewEntity

Task-number: QTBUG-78313
Change-Id: I1dc6d227cf9009f6fbd3230093c7a7a94fb05ae3
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>