Expose txinwitness for coinbase in JSON form

txinwitness is used as the witness commitment nonce so is necessary if
reconstructing block data from RPC data.

src/core_write.cpp

@@ -198,13 +198,13 @@ void TxToUniv(const CTransaction& tx, const uint256& hashBlock, UniValue& entry,
             o.pushKV("asm", ScriptToAsmStr(txin.scriptSig, true));
             o.pushKV("hex", HexStr(txin.scriptSig.begin(), txin.scriptSig.end()));
             in.pushKV("scriptSig", o);
-            if (!tx.vin[i].scriptWitness.IsNull()) {
-                UniValue txinwitness(UniValue::VARR);
-                for (const auto& item : tx.vin[i].scriptWitness.stack) {
-                    txinwitness.push_back(HexStr(item.begin(), item.end()));
-                }
-                in.pushKV("txinwitness", txinwitness);
+        }
+        if (!tx.vin[i].scriptWitness.IsNull()) {
+            UniValue txinwitness(UniValue::VARR);
+            for (const auto& item : tx.vin[i].scriptWitness.stack) {
+                txinwitness.push_back(HexStr(item.begin(), item.end()));
             }
+            in.pushKV("txinwitness", txinwitness);
         }
         in.pushKV("sequence", (int64_t)txin.nSequence);
         vin.push_back(in);