correctly calculate liquidity using LiquidityMath library

contracts/AutoRedemption.sol

@@ -10,6 +10,7 @@ import {IRedeemable} from "contracts/interfaces/IRedeemable.sol";
 import {ISmartVaultManager} from "contracts/interfaces/ISmartVaultManager.sol";
 import {IUniswapV3Pool} from "contracts/interfaces/IUniswapV3Pool.sol";
 import {IQuoter} from "contracts/interfaces/IQuoter.sol";
+import {LiquidityMath} from "src/uniswap/LiquidityMath.sol";
 import {TickMath} from "src/uniswap/TickMath.sol";
 import {LiquidityAmounts} from "src/uniswap/LiquidityAmounts.sol";
 import {IERC20} from
@@ -109,7 +110,7 @@ contract AutoRedemption is AutomationCompatibleInterface, FunctionsClient, Confi
                 );
             } else {
                 (, int128 _liquidityNet,,,,,,) = pool.ticks(_lowerTick);
-                _liquidity += uint128(_liquidityNet);
+                _liquidity = LiquidityMath.addDelta(_liquidity, _liquidityNet);
                 (_amount0,) = LiquidityAmounts.getAmountsForLiquidity(
                     _sqrtPriceX96,
                     TickMath.getSqrtRatioAtTick(_lowerTick),

contracts/uniswap/LiquidityMath.sol

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+pragma solidity >=0.5.0;
+
+/// @title Math library for liquidity
+library LiquidityMath {
+    /// @notice Add a signed liquidity delta to liquidity and revert if it overflows or underflows
+    /// @param x The liquidity before change
+    /// @param y The delta by which liquidity should be changed
+    /// @return z The liquidity delta
+    function addDelta(uint128 x, int128 y) internal pure returns (uint128 z) {
+        if (y < 0) {
+            require((z = x - uint128(-y)) < x, 'LS');
+        } else {
+            require((z = x + uint128(y)) >= x, 'LA');
+        }
+    }
+}