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
```
{
    return RPCHelpMan{
        "createwallet",
        "\nCreates and loads a new wallet.\n",
        {
            {"wallet_name", RPCArg::Type::STR, RPCArg::Optional::NO, "The name for the new wallet. If this is a path, the wallet will be created at the path location."},
            {"disable_private_keys", RPCArg::Type::BOOL,  "false", "Disable the possibility of private keys (only watchonlys are possible in this mode)."},
            {"blank", RPCArg::Type::BOOL,  "false", "Create a blank wallet. A blank wallet has no keys or HD seed. One can be set using sethdseed."},
            {"passphrase", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "Encrypt the wallet with this passphrase."},
            {"avoid_reuse", RPCArg::Type::BOOL,  "false", "Keep track of coin reuse, and treat dirty and clean coins differently with privacy considerations in mind."},
            {"descriptors", RPCArg::Type::BOOL,  "false", "Create a native descriptor wallet. The wallet will use descriptors internally to handle address creation"},
            {"load_on_startup", RPCArg::Type::BOOL,  "null", "Save wallet name to persistent settings and load on startup. True to add wallet to startup list, false to remove, null to leave unchanged."},
        },
        RPCResult{
            RPCResult::Type::OBJ, "", "",
            {
                {RPCResult::Type::STR, "name", "The wallet name if created successfully. If the wallet was created using a full path, the wallet_name will be the full path."},
                {RPCResult::Type::STR, "warning", "Warning message if wallet was not loaded cleanly."},
            }
        },
        RPCExamples{
            HelpExampleCli("createwallet", "\"testwallet\"")
            + HelpExampleRpc("createwallet", "\"testwallet\"")
        },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    WalletContext& context = EnsureWalletContext(request.context);
    uint64_t flags = 0;
    if (!request.params[1].isNull() && request.params[1].get_bool()) {