[REG 6.6.1 -> 6.7] rendering svg causes division by zero in getRadialGradientValues

1. Have a build of Qt configured with "-sanitize undefined".
2. Build the attached project with that.
3. Run the resulting binary with the attached svg file as parameter.
   The sanitizer will show a division by zero:

   /home/qtrob/dev/src/qt-dev_12.21-base_imageformats_svg/qtbase/src/gui/painting/qdrawhelper.cpp:3416:18: runtime error: division by zero
   SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/qtrob/dev/src/qt-dev_12.21-base_imageformats_svg/qtbase/src/gui/painting/qdrawhelper.cpp:3416:18 in
   

Google's oss-fuzz found this as issue 63780. Their report is public. It went to "Verified" state in November but I can still reproduce the issue with Qt's latest sources.