Nimiq: Remote crash via off-by-one signer bounds check in proposal buffer

nimiq/core-rs-albatross is a Rust implementation of the Nimiq Proof-of-Stake protocol based on the Albatross consensus algorithm. Prior to version 1.3.0, an untrusted peer could crash a validator by publishing a signed tendermint proposal message where signer == validators.num_validators(). ProposalSender::send uses > instead of >= for the signer bounds check, so the equality case passes and reaches validators.get_validator_by_slot_band(signer), which panics with an out-of-bounds index before any signature verification runs. This issue has been fixed in version 1.3.0.