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) {
```
*/
CWalletScanResult CWalletScanForWalletTransactions(const uint256& start_block, int start_height, stdoptional<int> max_height, const WalletRescanReserver& reserver, bool fUpdate, const bool save_progress)
{
    constexpr auto INTERVAL_TIME{60s};
    auto current_time{reserver.now()};
    auto start_time{reserver.now()};
    assert(reserver.isReserved());
    uint256 block_hash = start_block;
    ScanResult result;
    WalletLogPrintf("Rescan started from block %s...\n", start_block.ToString());
    fAbortRescan = false;
    ShowProgress(strprintf("%s " + _("Rescanning…").translated, GetDisplayName()), 0); // show rescan progress in GUI as dialog or on splashscreen, if rescan required on startup (e.g. due to corruption)
    uint256 tip_hash = WITH_LOCK(cs_, return GetLastBlockHash());
    uint256 end_hash = tip_hash;
    if (max_height) chain().findAncestorByHeight(tip_hash, *max_height, FoundBlock().hash(end_hash));
    double progress_begin = chain().guessVerificationProgress(block_hash);
    double progress_end = chain().guessVerificationProgress(end_hash);
    double progress_current = progress_begin;
    int block_height = start_height;
    while (!fAbortRescan && !chain().shutdownRequested()) {
        if (progress_end - progress_begin > 0.0) {
            m_scanning_progress = (progress_current - progress_begin) / (progress_end - progress_begin);
        } else { // avo
            m_scanning_progress = 0;
        }
        if (block_height % 100 == 0 && progress_end - progress_begin > 0.0) {
            ShowProgress(strprintf("%s " + _("Rescanning…").translated, GetDisplayName()), stdmax(1, stdmin(99, (int)(m_scanning_progress * 100))));
        }
        bool next_interval = reserver.now() >= current_time + INTERVAL_TIME;
        if (next_interval) {