bug: SNOS fails on blocks with 0 txs

[apoorvsadana]

SNOS version:

662d170

Current behavior:

Code panics here if the block has 0 txs in it.

Expected behavior:

Sepolia never has 0 blocks so maybe this is fine but for app chains like Pragma, this is possible and it would be nice to allow this.

Steps to reproduce:

Setting up pathfinder with Madara can be multiple steps. We've a makefile here which makes life easier but I think for this case, it might be easier to start with this pathfinder state and trying to run SNOS on block 1782
pathfinder.zip