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

[saitofun]

What would you like to be added

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

• Add unit tests to cover L58-L59
• Add unit tests to cover L71-L72
• Add unit tests to cover L97-L98
• Add unit tests to cover L125-L126
• Add unit tests to cover L132
• Add unit tests to cover L155
• Add unit tests to cover L178
• Add unit tests to cover L209-L210
• Add unit tests to cover L221
• Add unit tests to cover L224
• Add unit tests to cover L240
• Add unit tests to cover L243
• Add unit tests to cover L257
• Add unit tests to cover L260
• Add unit tests to cover L276
• Add unit tests to cover L279
• Add unit tests to cover L294-L296
• Add unit tests to cover L298-L300
• Add unit tests to cover L303-L308
• Add unit tests to cover L310
• Add unit tests to cover L321