KinematicBody colliding with meshes of a GridMap throws recover_from_penetration errors

[Miziziziz]

Godot version: 3.2.2.stable

OS/device including version: Windows 10

Issue description:
When a KinematicBody moves through a Gridmap on the same layer, this error is thrown constantly:
recover_from_penetration: Condition "shape_idx < 0 || shape_idx >= cs->getNumChildShapes()" is true. Returned: false
<C++ Source> modules/bullet/space_bullet.cpp:1249 @ recover_from_penetration()
KinematicBody.gd:5 @ _physics_process()

This error shouldn't be thrown, the Gridmap has no colliders or physics on it, it's purely graphical.

Steps to reproduce:
Have a kinematic body use move_and_collide/slide to move through a Gridmap tile.
Example video attached:
ExampleVIdeo.zip

Minimal reproduction project:

Physics Error repro.zip

[madmiraal]

This is not actually a physics problem, because it's correctly identifying that the StaticBody associated with the Mesh item has no CollisionShape. It's a problem with MeshLibraries (and related to #11888 which is about not being able to add shapes to a Mesh in a MeshLibrary). Basically, if the MeshLibrary Item has no shapes, it shouldn't be creating an associated StaticBody.

[laverneth]

It happened to me without StaticBodies, only "visual tiles". I "solved" the issue by deactivating the collision layers of the purely graphical gridmap

[rburing]

The case of a compound collision shape with zero child shapes was being treated as an error in recover_from_penetration, causing an early return from the function, which could cause the recovery from other shapes to be skipped. In fact recovering from a compound collision shape with zero child shapes is very easy: just ignore it. I implemented this in #59864 because the previous early return caused a pretty bad bug (see the issue linked there). Hence, this issue here can be closed as well.

I agree with @madmiraal that it would be better if GridMap somehow would not create static bodies without shapes. This should be discussed in a separate issue.