Merge bitcoin/bitcoin#27271: RPC: Fix fund transaction crash when at 0-value, 0-fee

d7cc503843 Fix fund transaction case at 0-value, 0-fee (Greg Sanders)

Pull request description:

  and when no inputs are pre-selected.

  triggered via:

  walletcreatefundedpsbt '[]' '[{"data": "deadbeef"}]' 0 '{"fee_rate": "0"}'

ACKs for top commit:
  achow101:
    ACK d7cc503843
  josibake:
    ACK https://github.com/bitcoin/bitcoin/pull/27271/commits/d7cc503843769b789dc5f031b4ddc75d555ba980
  furszy:
    Crashes sucks code ACK d7cc5038

Tree-SHA512: 3f5e10875666aaf52c11d6a38b951aa75d0cbe684cc7f904e199f7a864923bf31d03a654687f8b746cae0eebb886a799bff2c6d200699438480d4c0ff8785f3a

test/functional/rpc_psbt.py

@@ -941,6 +941,9 @@ class PSBTTest(BitcoinTestFramework):
         assert_equal(self.nodes[0].finalizepsbt(psbt.to_base64()),
             {'hex': '0200000001dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd0000000000000000000100000000000000000000000000', 'complete': True})
 
+        self.log.info("Test we don't crash when making a 0-value funded transaction at 0 fee without forcing an input selection")
+        assert_raises_rpc_error(-4, "Transaction requires one destination of non-0 value, a non-0 feerate, or a pre-selected input", self.nodes[0].walletcreatefundedpsbt, [], [{"data": "deadbeef"}], 0, {"fee_rate": "0"})
+
 
 if __name__ == '__main__':
     PSBTTest().main()