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) {
```
ConnectScriptPubKeyManNotifiers();
    NotifyCanGetAddressesChanged();
    WalletLogPrintf("Wallet migration complete.\n");
    return true;
}
bool DoMigration(CWallet& , WalletContext& context, bilingual_str& error, MigrationResult& res) EXCLUSIVE_LOCKS_REQUIRED(.cs_)
{
    AssertLockHeld(.cs_);
    // Get all of the s from the legacy 
    stdoptional<MigrationData> data = .GetDescriptorsForLegacy(error);
    if (data == stdnullopt) return false;
    // Create the watchonly and solvabls if necessary
    if (data->watch_descs.size() > 0 || data->solvable_descs.size() > 0) {
        DatabaseOptions options;
        options.require_existing = false;
        options.require_create = true;
        // Make ths
        options.create_flags = WALLET_FLAG_DISABLE_PRIVATE_KEYS | WALLET_FLAG_BLANK_WALLET | WALLET_FLAG_DESCRIPTORS;
        if (.IsWalletFlagSet(WALLET_FLAG_AVOID_REUSE)) {
            options.create_flags |= WALLET_FLAG_AVOID_REUSE;
        }
        if (.IsWalletFlagSet(WALLET_FLAG_KEY_ORIGIN_METADATA)) {
            options.create_flags |= WALLET_FLAG_KEY_ORIGIN_METADATA;
        }
        if (data->watch_descs.size() > 0) {
            .WalletLogPrintf("Making a new wa containing the watched scripts\n");
            DatabaseStatus status;
            stdvector<bilingual_str> warnings;
            stdstring _name = .GetName() + "_watchonly";
            data->watchonly_ = CreateWallet(context, _name, stdnullopt, options, status, error, warnings);