Panic when synchronizing against a testnet with different radon operators

[tmpolaczyk]

Given a recent change of Radon operator codes, blocks from testnet-4 should be marked as invalid by the current master branch. The exact cause is this unwrap from the witnet_rad crate:

witnet-rust/rad/src/operators/array.rs

Line 46 in f5be516

subscript.push(unpack_radon_call(arg).unwrap())

But there are many more similar unwraps in that crate. Ideally we should replace all the unwraps with returning a result, and add tests so this does not happen again.

[aesedepece]

Agreed, all those unwraps should be replaced with ? operator short-circuiting, or .try_fold() or .map().collect() if one wants to go functional.

[tmpolaczyk]

The unwraps were removed, but the tests are still missing. We need to test all the branches of unpack_radon_script, unpack_radon_call, unpack_compound_call and unpack_subscript.

[aesedepece]

Are we OK to close this?

[tmpolaczyk]

Only if there are tests