The problem is there are 1953 points that aren't assigned to any vertex group. They are all in the cat models, and they all happen to be loose verts too, which makes them easy to clean up. In Blender, unhide everything, select everything, enter mesh edit mode, select all the vertices, and do Mesh > Clean Up > Delete Loose. You should see a message: "Removed: 1953 vertices, ...".
OTOH, if you didn't intend to export the cat models, you just need to re-export using "Selection Only" or something.
OTOH, if you didn't intend to export the cat models, you just need to re-export using "Selection Only" or something.