The reduceStakeTo function does not have any check to prevent it from being called when staker.amountStaked is zero. This means if a stakers amountStaked is zero, the function can still be called, and it would set the amountStaked to the target value, which could result in unintended behavior.
https://github.com/code-423n4/2024-05-arbitrum-foundation/blob/6f861c85b281a29f04daacfe17a2099d7dad5f8f/src/rollup/RollupCore.sol#L300-L310
staker.amountStaked is 0 then the call should be reverted.
require(current > 0,"zero amount staked");
