co-circom: generate-proof: groth16: testcase panics

[romanmarkusholler]

using 419488b

and the artifacts from panic.zip

cargo run --release --bin co-circom -- generate-proof groth16 --witness test_vectors/panic/witness.wtns.0.shared --zkey test_vectors/panic/circuit.zkey --protocol REP3 --curve BN254 --config ../configs/party1.toml --out proof.0.json --public-input public_input.json &
cargo run --release --bin co-circom -- generate-proof groth16 --witness test_vectors/panic/witness.wtns.1.shared --zkey test_vectors/panic/circuit.zkey --protocol REP3 --curve BN254 --config ../configs/party2.toml --out proof.1.json &
cargo run --release --bin co-circom -- generate-proof groth16 --witness test_vectors/panic/witness.wtns.2.shared --zkey test_vectors/panic/circuit.zkey --protocol REP3 --curve BN254 --config ../configs/party3.toml --out proof.2.json

leads to

thread 'main' panicked at collaborative-circom/co-groth16/src/groth16.rs:220:46:
range end index 1001 out of range for slice of length 587