Added getNullFillResults

packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol

@@ -107,7 +107,7 @@ contract MixinExchangeCore is
         );
         if (status != uint8(Status.SUCCESS)) {
             emit ExchangeStatus(uint8(status), orderInfo.orderHash);
-            return fillResults;
+            return getNullFillResults();
         }
 
         // Settle order

packages/contracts/src/contracts/current/protocol/Exchange/libs/LibFillResults.sol

@@ -50,4 +50,19 @@ contract LibFillResults is
         totalFillResults.makerFeePaid = safeAdd(totalFillResults.makerFeePaid, singleFillResults.makerFeePaid);
         totalFillResults.takerFeePaid = safeAdd(totalFillResults.takerFeePaid, singleFillResults.takerFeePaid);
     }
+
+    /// @dev Returns a null fill results struct
+    function getNullFillResults()
+        internal
+        pure
+        returns (FillResults memory)
+    {
+        // returns zeroed out FillResults instance
+        return FillResults({
+            makerAssetFilledAmount: 0,
+            takerAssetFilledAmount: 0,
+            makerFeePaid: 0,
+            takerFeePaid: 0
+        });
+    }
 }