Running master 4d661ba:
```
src/bitcoin-cli combinepsbt [""] or src/bitcoin-cli combinepsbt []
```

```
  * frame #0: 0x000000010016054a bitcoind`PartiallySignedTransaction::PartiallySignedTransaction(PartiallySignedTransaction const&) [inlined] boost::optional_detail::optional_base<CMutableTransaction>::is_initialized(this=0x0000000000000000) const at optional.hpp:394 [opt]
    frame #1: 0x000000010016054a bitcoind`PartiallySignedTransaction::PartiallySignedTransaction(PartiallySignedTransaction const&) [inlined] boost::optional_detail::optional_base<CMutableTransaction>::optional_base(this=<unavailable>, rhs=0x0000000000000000) at optional.hpp:196 [opt]
    frame #2: 0x0000000100160542 bitcoind`PartiallySignedTransaction::PartiallySignedTransaction(PartiallySignedTransaction const&) [inlined] boost::optional<CMutableTransaction>::optional(this=0x000070000b9fe7c0, (null)=0x0000000000000000) at optional.hpp:958 [opt]
    frame #3: 0x0000000100160542 bitcoind`PartiallySignedTransaction::PartiallySignedTransaction(PartiallySignedTransaction const&) [inlined] boost::optional<CMutableTransaction>::optional(this=0x000070000b9fe7c0, (null)=0x0000000000000000) at optional.hpp:958 [opt]
    frame #4: 0x0000000100160542 bitcoind`PartiallySignedTransaction::PartiallySignedTransaction(this=0x000070000b9fe7c0, psbt_in=0x0000000000000000) at sign.h:576 [opt]
    frame #5: 0x0000000100142ae5 bitcoind`combinepsbt(JSONRPCRequest const&) [inlined] PartiallySignedTransaction::PartiallySignedTransaction(this=0x000070000b9fe700, psbt_in=<unavailable>) at sign.h:576 [opt]
    frame #6: 0x0000000100142ae0 bitcoind`combinepsbt(request=<unavailable>) at rawtransaction.cpp:1526 [opt]
    frame #7: 0x0000000100170f0a bitcoind`CRPCTable::execute(this=<unavailable>, request=0x000070000b9fead0) const at server.cpp:557 [opt]
```
if (g_txindex && !blockindex) {
        f_txindex_ready = g_txindex->BlockUntilSyncedToCurrentChain();
    }
    CTransactionRef tx;
    uint256 hash_block;
    if (!GetTransaction(hash, tx, Params().GetConsensus(), hash_block, blockindex)) {
        std::string errmsg;
        if (blockindex) {
            if (!(blockindex->nStatus & BLOCK_HAVE_DATA)) {
                throw JSONRPCError(RPC_MISC_ERROR, "Block not available");
            }
            errmsg = "No such transaction found in the provided block";
        } else if (!g_txindex) {
            errmsg = "No such mempool transaction. Use -txindex to enable blockchain transaction queries";
        } else if (!f_txindex_ready) {
            errmsg = "No such mempool transaction. Blockchain transactions are still in the process of being indexed";
        } else {
            errmsg = "No such mempool or blockchain transaction";
        }
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, errmsg + ". Use gettransaction for wallet transactions.");
    }
    if (!fVerbose) {
        return EncodeHexTx(*tx, RPCSerializationFlags());
    }
    UniValue result(UniValue::VOBJ);
    if (blockindex) result.pushKV("in_active_chain", in_active_chain);
    TxToJSON(*tx, hash_block, result);
    return result;
}
static UniValue gettxoutproof(const JSONRPCRequest& request)