Attempting to load a wallet with an unknown descriptor causes a fatal error:

```
2022-09-06T01:51:06Z init message: Loading wallet…
2022-09-06T01:51:06Z [descriptor] Invalid descriptor: Can only have tr at top level: iostream error
2022-09-06T01:51:06Z [descriptor] Invalid descriptor: Can only have tr at top level: iostream error
2022-09-06T01:51:06Z [descriptor] Setting spkMan to active: id = 50e6032b4d1d62c020ebb6a4d0c8fafc6f01ea80f4d2a41c1a256086611636e9, type = legacy, internal = false
2022-09-06T01:51:06Z [descriptor] Setting spkMan to active: id = 7f709abbde61e8c253798375692bf41202e625ed74a65f9474d464be34fb2870, type = p2sh-segwit, internal = false
2022-09-06T01:51:06Z [descriptor] Setting spkMan to active: id = 2dc6c34099e0ca1235fc990a51042967ecbc8c8ac57062f964739cba2f451be8, type = bech32, internal = false
2022-09-06T01:51:06Z [descriptor] Setting spkMan to active: id = 8d3c63ea1ac9936e789713dc8bae857d328ff029ab9392e67c716752e9b11b0c, type = bech32m, internal = false
2022-09-06T01:51:06Z [descriptor] Releasing wallet
2022-09-06T01:51:06Z 

************************
EXCEPTION: St12out_of_range       
map::at       
bitcoin in Runaway exception       



************************
EXCEPTION: St12out_of_range       
map::at       
bitcoin in Runaway exception       

bitcoin-qt: ./checkqueue.h:204: CCheckQueue<CScriptCheck>::~CCheckQueue() [T = CScriptCheck]: Assertion `m_worker_threads.empty()' failed.
Aborted
```

> A fatal error occurred. Bitcoin Core can no longer continue safely and will quit.

To reproduce, a quick hack:

```c++
--- a/src/script/descriptor.cpp
+++ b/src/script/descriptor.cpp
@@ -1408,7 +1408,7 @@ std::unique_ptr<DescriptorImpl> ParseScript(uint32_t& key_exp_index, Span<const
         error = "Can only have addr() at top level";
         return nullptr;
     }
-    if (ctx == ParseScriptContext::TOP && Func("tr", expr)) {
+    if (ctx == ParseScriptContext::TOP && Func("trx", expr)) {
         auto arg = Expr(expr);
         auto internal_key = ParsePubkey(key_exp_index, arg, ParseScriptContext::P2TR, out, error);
         if (!internal_key) {
```
// TODO add account parameter
        int account = 0;
        UniValue signer_res = signer.GetDescriptors(account);
        if (!signer_res.isObject()) throw stdruntime_error(stdstring(__func__) + " Unexpected result");
        for (bool internal  {false, true}) {
            const UniValue& _vals = find_value(signer_res, internal ? "internal"  "receive");
            if (!_vals.isArray()) throw stdruntime_error(stdstring(__func__) + " Unexpected result");
            for (const UniValue& desc_val  _vals.get_array().getValues()) {
                const stdstring& desc_str = desc_val.getValStr();
                FlatSigningProvider keys;
                stdstring desc_error;
                stdunique_ptr<Descriptor> desc = Parse(desc_str, keys, desc_error, 
                if (desc == nullptr) {
                    throw stdruntime_error(stdstring(__func__) + " Invalid  \"" + desc_str + "\" (" + desc_error + ")");
                }
                if (!desc->GetOutputType()) {
                    continue;
                }
                OutputType t =  *desc->GetOutputType();
                auto spk_manager = stdunique_ptr<ExternalSignerScriptPubKeyMan>(new ExternalSignerScriptPubKeyMan(*this));
                spk_manager->SetupDescriptor(stdmove(desc));
                uint256 id = spk_manager->GetID();
                m_spk_managers[id] = stdmove(spk_manager);
                AddActiveScriptPubKeyMan(id, t, internal);
            }
        }
    }
}
void CWalletAddActiveScriptPubKeyMan(uint256 id, OutputType type, bool internal)
{