Fix crash when executing `TubeTrailMesh.get_faces()` with GLES3

drivers/gles3/storage/mesh_storage.cpp

@@ -352,6 +352,10 @@ RS::SurfaceData MeshStorage::mesh_get_surface(RID p_mesh, int p_surface) const {
 		sd.attribute_data = Utilities::buffer_get_data(GL_ARRAY_BUFFER, s.attribute_buffer, s.attribute_buffer_size);
 	}
 
+	if (s.skin_buffer != 0) {
+		sd.skin_data = Utilities::buffer_get_data(GL_ARRAY_BUFFER, s.skin_buffer, s.skin_buffer_size);
+	}
+
 	sd.vertex_count = s.vertex_count;
 	sd.index_count = s.index_count;
 	sd.primitive = s.primitive;