fix a bug in crypto helpers

Change-Id: I56829c78d95802aa013f1e0dc684fefb106df1f6
diff --git a/src/detail/crypto-helpers.cpp b/src/detail/crypto-helpers.cpp
index d72d7bf..3142268 100644
--- a/src/detail/crypto-helpers.cpp
+++ b/src/detail/crypto-helpers.cpp
@@ -376,7 +376,6 @@
                                     associatedData, associatedDataSize, block.get(tlv::AuthenticationTag).value(),
                                     key, block.get(tlv::InitializationVector).value(), result.data());
   if (resultLen != encryptedPayloadBlock.value_size()) {
-    return Buffer();
     NDN_THROW(std::runtime_error("Error when decrypting the AES Encrypted Block: "
                                  "Decrypted payload is of an unexpected size"));
   }