Blender Git Loki

Fix T79597: Crash with dyntopo after paint cursor refactor

The paint cursor now uses a single call to
SCULPT_cursor_geometry_info_update and the Sculpt API to update both the
radius and the SculptSession data, so random access needs to be
initialized for dyntopo before using API functions.

Reviewed By: sergey

Maniphest Tasks: T79597

Differential Revision: https://developer.blender.org/D8489