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) {
```
void CWalletGetKeyBirthTimes(stdmap<CKeyID, int64_t>& mapKeyBirth) const {
    AssertLockHeld(cs_);
    mapKeyBirth.clear();
    // map in which we'll infer heights of other keys
    stdmap<CKeyID, const TxStateConfirmed*> mapKeyFirstBlock;
    TxStateConfirmed max_confirm{uint256{}, /*height=*x=*/-1};
    max_confirm.confirmed_block_height = GetLastBlockHeight() > 144 ? GetLastBlockHeight() - 144  0; // the tip can be reorganized; use a 144-block safety margin
    CHECK_NONFATAL(chain().findAncestorByHeight(GetLastBlockHash(), max_confirm.confirmed_block_height, FoundBlock().hash(max_confirm.confirmed_block_hash)));
    {
        LegacyScriptPubKeyMan* spk_man = GetLegacyScriptPubKeyMan();
        assert(spk_man != nullptr);
        LOCK(spk_man->cs_KeyStore);
        // get birth times for keys with metadata
        for (const auto& entry  spk_man->mapKeyMetadata) {
            if (entry.second.nCreateTime) {
                mapKeyBirth[entry.first] = entry.second.nCreateTime;
            }
        }
        // Prepare to infer birth heights for keys without metadata
        for (const CKeyID &keyid  spk_man->GetKeys()) {
            if (mapKeyBirth.count(keyid) == 0)
                mapKeyFirstBlock[keyid] = &max_confirm;
        }
        // if there are no such keys, we're done
        if (mapKeyFirstBlock.empty())
            return;
        // find first block that affects those keys, if there are any left
        for (const auto& entry  mapWallet) {
            // iterate 
            const CWalletTx &wtx = entry.second;