fix conditions

Author: nialexsan

cadence/contracts/TidalProtocol.cdc

@@ -610,7 +610,7 @@ access(all) contract TidalProtocol {
             let uintWithdrawBorrowFactor = TidalProtocolUtils.ufix64ToUInt256(self.borrowFactor[withdrawType]!, decimals: TidalProtocolUtils.decimals)
 
             let maybeBalance = position.balances[withdrawType]
-                if maybeBalance?.direction == BalanceDirection.Debit {
+                if maybeBalance == nil || maybeBalance!.direction == BalanceDirection.Debit {
                     // If the position doesn't have any collateral for the withdrawn token, we can just compute how much
                     // additional effective debt the withdrawal will create.
                     effectiveDebtAfterWithdrawal = balanceSheet.effectiveDebt +
@@ -831,7 +831,7 @@ access(all) contract TidalProtocol {
             let uintDepositBorrowFactor = TidalProtocolUtils.ufix64ToUInt256(self.borrowFactor[depositType]!, decimals: TidalProtocolUtils.decimals)
             let uintDepositCollateralFactor = TidalProtocolUtils.ufix64ToUInt256(self.collateralFactor[depositType]!, decimals: TidalProtocolUtils.decimals)
             let maybeBalance = position.balances[depositType]
-                if maybeBalance?.direction == BalanceDirection.Credit {
+                if maybeBalance == nil || maybeBalance!.direction == BalanceDirection.Credit {
                     // If there's no debt for the deposit token, we can just compute how much additional effective collateral the deposit will create.
                     effectiveCollateralAfterDeposit = balanceSheet.effectiveCollateral +
                         TidalProtocolUtils.mul(TidalProtocolUtils.mul(uintDepositAmount, uintDepositPrice), uintDepositCollateralFactor)