Adjust gas check

contracts/GnosisSafe.sol

@@ -140,9 +140,9 @@ contract GnosisSafe
             txHash = keccak256(txHashData);
             checkSignatures(txHash, txHashData, signatures, true);
         }
-        // We require some gas to emit the events (2500) after the execution and some to perform code until the execution (500)
-        // We also increase the amount required by 1/64 to counteract potential shortings because of EIP-150
-        require(gasleft() - 3000 >= safeTxGas * 65 / 64, "Not enough gas to execute safe transaction");
+        // We require some gas to emit the events (at least 2500) after the execution and some to perform code until the execution (500)
+        // We also include the 1/64 in the check that is not send along with a call to counteract potential shortings because of EIP-150
+        require(gasleft() >= (safeTxGas * 64 / 63).max(safeTxGas + 2500) + 500, "Not enough gas to execute safe transaction");
         // Use scope here to limit variable lifetime and prevent `stack too deep` errors
         {
             uint256 gasUsed = gasleft();

contracts/external/GnosisSafeMath.sol

@@ -64,4 +64,12 @@ library GnosisSafeMath {
     require(b != 0);
     return a % b;
   }
+
+
+  /**
+  * @dev Returns the largest of two numbers.
+  */
+  function max(uint256 a, uint256 b) internal pure returns (uint256) {
+    return a >= b ? a : b;
+  }
 }