Bad type cast on a StorageMap return results in a vague error message

[roschler]

In the code below, I used the wrong key field to retrieve a StorageMap value. This result in a bad cast attempt, trying to cast a BigInteger value to a UInt160 value. This produced a strange VM exception that doesn't indicate the actual error.

Here's the code:

        private static UInt160 getOwner()
        {
            var ownerVal =  (UInt160) ContractMetadata.Get(VARNAME_WRONG_KEY_FIELD_NAME);

            // Convert null to UInt160.Zero.
            if (ownerVal == null)
                return UInt160.Zero;
            return ownerVal;
        }

VARNAME_WRONG_KEY_FIELD_NAME belongs to a BigInteger value in the storage map, not a UInt160.

Here's the error message:

Engine State Fault: An unhandled exception was thrown. (���	ZT� ����`��cs�?؏ [VMUnhandledException]