Fix MultiMesh errors in editor and resource duplication

[ydeltastar]

The buffer property of a MultiMesh can't be set when there are no instances, but no instances are the default so it causes issues with the editor and resource duplication.

Trying to set the property in the editor gives this error:

rendering/renderer_rd/storage_rd/mesh_storage.cpp:1935 - Condition "p_buffer.size() != (multimesh->instances * (int)multimesh->stride_cache)" is true.

When the MultiMesh is a resource_local_to_scene, the engine gives this error every time it instantiates a scene with it:

Buffer argument is not a valid buffer of any type.

• Fixes: Instancing MultiMesh with local to scene flag set throws Vulkan buffer argument error #68592

[adadgio]

Hi ! Any ETA for this issue to be merged ?

[clayjohn]

Looks good to me. Tested locally and I didn't notice any issues. I confirmed that the MRP is fixed

[akien-mga]

Thanks!