Create a wallet as follows:

```sh
$ bitcoin-cli createwallet "watchonly" true
$ bitcoin-cli -rpcwallet=watchonly getwalletinfo
{
   ...
   "private_keys_enabled": false
}
```

The following should fail, but doesn't:

```sh
$ bitcoin-cli -rpcwallet=watchonly encryptwallet 1234
wallet encrypted; The keypool has been flushed and a new HD seed was generated (if you are using HD). You need to make a new backup.
```

It partially fails silently, because it doesn't actually add a seed. But it does ask for a password when calling `dumpwallet`, which doesn't make sense because we currently don't encrypt anything other than private keys.  
"                             transaction, just kept in your wallet."},
                    {"subtractfeefromamount", RPCArg::Type::BOOL,  "false", "The fee will be deducted from the amount being sent.\n"
            "                             The recipient will receive less bitcoins than you enter in the amount field."},
                    {"replaceable", RPCArg::Type::BOOL,  "fallback to wallet's default", "Allow this transaction to be replaced by a transaction with higher fees via BIP 125"},
                    {"conf_target", RPCArg::Type::NUM,  "fallback to wallet's default", "Confirmation target (in blocks)"},
                    {"estimate_mode", RPCArg::Type::STR,  "UNSET", "The fee estimate mode, must be one of:\n"
            "       \"UNSET\"\n"
            "       \"ECONOMICAL\"\n"
            "       \"CONSERVATIVE\""},
                },
                RPCResult{
            "\"txid\"                  (string) The transaction id.\n"
                },
                RPCExamples{
                    HelpExampleCli("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\" 0.1")
            + HelpExampleCli("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\" 0.1 \"donation\" \"seans outpost\"")
            + HelpExampleCli("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\" 0.1 \"\" \"\" true")
            + HelpExampleRpc("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\", 0.1, \"donation\", \"seans outpost\"")
                },
            }.ToString());
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    CTxDestination dest = DecodeDestination(request.params[0].get_str());
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
    }