add unit tests for `action/protocol/staking/protocol.go`

[saitofun]

What would you like to be added

add unit tests for action/protocol/staking/protocol.go

• [ ] Add unit tests to cover L517
• [ ] Add unit tests to cover L529-L530
• [ ] Add unit tests to cover L541-L543
• [ ] Add unit tests to cover L546
• [ ] Add unit tests to cover L548
• [ ] Add unit tests to cover L550
• [ ] Add unit tests to cover L552
• [ ] Add unit tests to cover L554
• [ ] Add unit tests to cover L556
• [ ] Add unit tests to cover L558
• [ ] Add unit tests to cover L560-L574