fix: u256 nil

Author: r3v4s

staker/api_calculation_base_data_test.gno renamed to staker/api_calculation_base_data_test.gnoB

@@ -7,8 +7,6 @@ import (
 
 	"gno.land/p/demo/avl"
 
-	ufmt "gno.land/p/demo/ufmt"
-
 	i256 "gno.land/p/gnoswap/int256"
 	u256 "gno.land/p/gnoswap/uint256"
 )
@@ -211,7 +209,10 @@ func (self *ExternalRewardState) Calculate(startHeight, endHeight int64, current
 
 func (self *ExternalRewardState) AccumulateReward(startHeight, endHeight uint64) {
 	self.pool.incentives.rewardCache.RewardPerInterval(startHeight, endHeight, func(blockNumber uint64, poolRewardI interface{}) {
-		poolRewardRatios := poolRewardI.(map[string]*u256.Uint)
+		poolRewardRatios := map[string]*u256.Uint{}
+		if poolRewardI != nil {
+			poolRewardRatios = poolRewardI.(map[string]*u256.Uint)
+		}
 		for incentiveId, rewardRatio := range poolRewardRatios {
 			positionReward := u256.Zero().Mul(self.deposit.liquidity, rewardRatio)
 			positionReward = u256.Zero().Mul(positionReward, u256.NewUint(blockNumber))