what small way does Bilbo manage to prevent a total disaster in the cave?

I took a look at the chapter again, I think it’s in chapter 4. The dwarves and Gandalf take shelter in a cave for the night. They also bring their ponies in. That night Bilbo has nightmares foreshadowing the coming events. Bilbo wakes up just in time to see a crack open in the cave and engulf the ponies. Goblins come out of this crack but not before Bilbo yells and warns them (that, I think, is how he helps). This gives Gandalf time to vanish and aid them through his magic.