Merge #12278: Add special error for genesis coinbase to getrawtransaction

ee11121 Add special error for genesis coinbase to gettransaction (MeshCollider)

Pull request description:

  Suggested by sipa here: https://botbot.me/freenode/bitcoin-core-dev/2018-01-23/?msg=96069825&page=2

  Just adds a special error message for the genesis block coinbase transaction when using `getrawtransaction`

Tree-SHA512: cd102c7983ec5457b299bff4b6db747d339fda157933a3ac54aec26b1e48b115aa68c1c9e6cb7a916f15c7786273ab558b2b20ab9768544d211e0ae9d1480e34

src/rpc/rawtransaction.cpp

@@ -147,6 +147,11 @@ UniValue getrawtransaction(const JSONRPCRequest& request)
     uint256 hash = ParseHashV(request.params[0], "parameter 1");
     CBlockIndex* blockindex = nullptr;
 
+    if (hash == Params().GenesisBlock().hashMerkleRoot) {
+        // Special exception for the genesis block coinbase transaction
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "The genesis block coinbase is not considered an ordinary transaction and cannot be retrieved");
+    }
+
     // Accept either a bool (true) or a num (>=1) to indicate verbose output.
     bool fVerbose = false;
     if (!request.params[1].isNull()) {