Have this warning while building current master (0bd4929cd00e91bf4137f43b097cd62f72f503e4) on one test machine.
```
wallet/rpcwallet.cpp: In function 'rescanblockchain()::<lambda(const RPCHelpMan&, const JSONRPCRequest&)>':
wallet/rpcwallet.cpp:3596:19: warning: '*((void*)& stop_height +4)' may be used uninitialized in this function [-Wmaybe-uninitialized]
 3596 |     Optional<int> stop_height;
      |                   ^~~~~~~~~~~
```
```
$ gcc --version
gcc (Gentoo 9.2.0-r2 p3) 9.2.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ uname -a
Linux red-box 4.19.72-gentoo #2 SMP Sun Sep 22 03:00:01 EEST 2019 x86_64 Intel(R) Pentium(R) CPU N3710 @ 1.60GHz GenuineIntel GNU/Linux
```
static RPCHelpMan psbtbumpfee() { return bumpfee_helper("psbtbumpfee"); }
static RPCHelpMan rescanblockchain()
{
    return RPCHelpMan{"rescanblockchain",
                "\nRescan the local blockchain for wallet related transactions.\n"
                "Note: Use \"getwalletinfo\" to query the scanning progress.\n",
                {
                    {"start_height", RPCArg::Type::NUM,  "0", "block height where the rescan should start"},
                    {"stop_height", RPCArg::Type::NUM, RPCArg::Optional::OMITTED_NAMED_ARG, "the last block height that should be scanned. If none is provided it will rescan up to the tip at return time of this call."},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::NUM, "start_height", "The block height where the rescan started (the requested height or 0)"},
                        {RPCResult::Type::NUM, "stop_height", "The height of the last rescanned block. May be null in rare cases if there was a reorg and the call didn't scan any blocks because they were already scanned in the background."},
                    }
                },
                RPCExamples{
                    HelpExampleCli("rescanblockchain", "100000 120000")
            + HelpExampleRpc("rescanblockchain", "100000, 120000")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{