Fix shadow mesh recursion.

drivers/gles3/storage/mesh_storage.cpp

@@ -743,6 +743,7 @@ String MeshStorage::mesh_get_path(RID p_mesh) const {
 }
 
 void MeshStorage::mesh_set_shadow_mesh(RID p_mesh, RID p_shadow_mesh) {
+	ERR_FAIL_COND_MSG(p_mesh == p_shadow_mesh, "Cannot set a mesh as its own shadow mesh.");
 	Mesh *mesh = mesh_owner.get_or_null(p_mesh);
 	ERR_FAIL_NULL(mesh);
 

scene/resources/mesh.cpp

@@ -2251,6 +2251,7 @@ Error ArrayMesh::lightmap_unwrap_cached(const Transform3D &p_base_transform, flo
 }
 
 void ArrayMesh::set_shadow_mesh(const Ref<ArrayMesh> &p_mesh) {
+	ERR_FAIL_COND_MSG(p_mesh == this, "Cannot set a mesh as its own shadow mesh.");
 	shadow_mesh = p_mesh;
 	if (shadow_mesh.is_valid()) {
 		RS::get_singleton()->mesh_set_shadow_mesh(mesh, shadow_mesh->get_rid());

servers/rendering/renderer_rd/storage_rd/mesh_storage.cpp

@@ -783,6 +783,7 @@ String MeshStorage::mesh_get_path(RID p_mesh) const {
 }
 
 void MeshStorage::mesh_set_shadow_mesh(RID p_mesh, RID p_shadow_mesh) {
+	ERR_FAIL_COND_MSG(p_mesh == p_shadow_mesh, "Cannot set a mesh as its own shadow mesh.");
 	Mesh *mesh = mesh_owner.get_or_null(p_mesh);
 	ERR_FAIL_NULL(mesh);