In batch cell verification, check if there are zero cells

Author: jtraglia

specs/_features/eip7594/polynomial-commitments-sampling.md

@@ -511,6 +511,10 @@ def verify_cell_kzg_proof_batch_impl(row_commitments: Sequence[KZGCommitment],
     n = FIELD_ELEMENTS_PER_CELL
     num_rows = len(row_commitments)
 
+    # Given zero cells, the result is true
+    if num_cells == 0:
+        return True
+
     # Step 1: Compute a challenge r and its powers r^0, ..., r^{num_cells-1}
     r = compute_verify_cell_kzg_proof_batch_challenge(
         row_commitments,
@@ -567,7 +571,6 @@ def verify_cell_kzg_proof_batch_impl(row_commitments: Sequence[KZGCommitment],
     ]))
 ```
 
-
 ### Cell cosets
 
 #### `coset_shift_for_cell`