🚀[FEA]: Add Support for Scenarios With No World Edges in Hybrid MeshGraphNet

[mnabian]

Is this a new feature, an improvement, or a change to existing functionality?

Improvement

How would you describe the priority of this feature request

Medium

Please provide a clear description of problem you would like to solve.

The Hybrid MeshGraphNet model is not currently designed to handle cases where the number of world edge features is zero. However, this is needed in a couple of scenarios:

1. A scenario where two objects collide. During their free flight phase, there are no world edges.
2. A scenario involving multi-step prediction within a one-step simulation. This is used for better training in nonlinear dynamics, such as a crash.

More context in #1123.

Describe any alternatives you have considered

No response