Crash when using raycast in tool while map is updated.

[StefanFabian]

When using our waypoint tool which internally uses a raycast from the scenemanager while new maps are published.
Rviz crashes reproducibly as soon as the tool touches the map area.

Your environment

• OS Version: e.g. Ubuntu 20.04
• ROS Distro: Noetic
• RViz, Qt, OGRE, OpenGl version as printed by rviz:

  [ INFO] [1683209782.510052557]: rviz version 1.14.20
  [ INFO] [1683209782.510134481]: compiled against Qt version 5.12.8
  [ INFO] [1683209782.510150195]: compiled against OGRE version 1.9.0 (Ghadamon)
  [ INFO] [1683209782.521403607]: Forcing OpenGl version 0.
  [ INFO] [1683209783.316236451, 124.903000000]: Stereo is NOT SUPPORTED
  [ INFO] [1683209783.316314813, 124.903000000]: OpenGL device: NVIDIA GeForce RTX 3060 Laptop GPU/PCIe/SSE2
  [ INFO] [1683209783.316342959, 124.903000000]: OpenGl version: 4,6 (GLSL 4,6).
  

• If source build, which git commit?
• System locale, i.e. the output of echo "$LANG $LC_NUMERIC": en_US.UTF-8 de_DE.UTF-8