The `Group` node causing instabilities in the simulation (Webots crashes)

[lukicdarkoo]

Describe the Bug The simulation bellow crashes in R2020b rev1 and R2021a, while it works fine in R2020a rev1. Changing the rotation parameter, or deleting boundingObject USE ToolShape2, or moving the Floor node out of the Group node makes the simulation work fine. Therefore, I am not sure what is causing the issue, but I suspect it is the Group node as the user managed to make the full simulation (this is just a minimal version) work when removed the Group node.

It may be related to #2420

Steps to Reproduce

Relavant .wbt file

``` #VRML_SIM R2021a utf8 WorldInfo { coordinateSystem "NUE" } Viewpoint { } TexturedBackground { } TexturedBackgroundLight { } DEF ENVIRONMENT Group { children [ Floor { } ] } DEF ROBOT3 UR10e { rotation 1 2.1577e-08 1.89076e-06 -1.5707953071795862 name "robot_3" toolSlot [ Solid { children [ SliderJoint { jointParameters JointParameters { } device [ LinearMotor { name "linear_motor1" } ] endPoint Solid { children [ DEF ToolShape2 Shape { appearance PBRAppearance { } geometry Box { size 0.1 0.1 0.1 } } ] name "solid (3)" boundingObject USE ToolShape2 physics Physics { } } } SliderJoint { jointParameters JointParameters { } device [ LinearMotor { name "linear_motor2" } ] endPoint Solid { } } DEF ToolShape1 Shape { appearance PBRAppearance { } geometry Box { size 0.1 0.1 0.1 } } ] boundingObject USE ToolShape1 physics Physics { density -1 mass 0.2 } } ] } ```

1. Save and run the code from the collapsable above

Expected behavior Should not crash

System

• Operating System: Windows 10
• Graphics Card: NVIDIA GeForce RTX 2060
• Webots version: R2020b rev1 and R2021a

[omichel]

Fixed in #2505.