Like @JR01 said - your issue was an object “Brian” that has an empty sprite, and Polygon collision shape (why?) and a Flip block. The strange combination of those three things was making the engine unhappy.
I set the Brian object to a rectangle collision for now to work around the issue, and I’ll see if I can figure out a workaround in the engine. In the meantime, only use polygon colliders where you really need them - they are complicated and slow compared to rectangles and circles.
If you do need a polygon shape, that’s fine too - just make sure your sprite has some pixels for the collision generator to make a shape from.