Tokio crash on macOS with "Top Functions" view

devfiler is crashing on macOS (Tahoe 26.3.1) in what seems to be a null pointer dereference in a Tokio worker thread:

```
Triggered by Thread: 23 tokio-runtime-worker

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: UNKNOWN_0xD at 0x0000000000000000
Exception Codes: 0x000000000000000d, 0x0000000000000000

Termination Reason: Namespace SIGNAL, Code 11, Segmentation fault: 11
Terminating Process: exc handler [89142]

Thread 23 Crashed:: tokio-runtime-worker
0 devfiler 0x10289e020 devfiler::ui::tabs::top_funcs::query_top_funcs::_$u7b$$u7b$closure$u7d$$u7d$::he6feae051a32a4e2 + 416 (top_funcs.rs:351) [inlined]
1 devfiler 0x10289e020 _$LT$tokio..runtime..blocking..task..BlockingTask$LT$T$GT$$u20$as$u20$core..future..future..Future$GT$::poll::h731dac7e2cd87dd2 + 528 (task.rs:42)
2 devfiler 0x102855ce6 tokio::runtime::task::core::Core$LT$T$C$S$GT$::poll::_$u7b$$u7b$closure$u7d$$u7d$::h0eb8a7fd47735f11 + 29 (core.rs:331) [inlined]
3 devfiler 0x102855ce6 tokio::loom::std::unsafe_cell::UnsafeCell$LT$T$GT$::with_mut::hcdb61f0a3209e039 + 29 (unsafe_cell.rs:16) [inlined]
4 devfiler 0x102855ce6 tokio::runtime::task::core::Core$LT$T$C$S$GT$::poll::hf076a201589d0dd3 + 29 (core.rs:320) [inlined]
5 devfiler 0x102855ce6 tokio::runtime::task::harness::poll_future::_$u7b$$u7b$closure$u7d$$u7d$::h77b90c48af23508d + 29 (harness.rs:499) [inlined]
6 devfiler 0x102855ce6 _$LT$core..panic..unwind_safe..AssertUnwindSafe$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$$LP$$RP$$GT$$GT$::call_once::h5f07ed0338524133 + 29 (unwind_safe.rs:272) [inlined]
7 devfiler 0x102855ce6 std::panicking::try::do_call::hed534c9cb12b1efa + 29 (panicking.rs:589) [inlined]
8 devfiler 0x102855ce6 std::panicking::try::hfa99f32d1aef35e2 + 29 (panicking.rs:552) [inlined]
9 devfiler 0x102855ce6 std::panic::catch_unwind::hf7d663814caafbfa + 29 (panic.rs:359) [inlined]
10 devfiler 0x102855ce6 tokio::runtime::task::harness::poll_future::h0f7713133ec0739d + 29 (harness.rs:487) [inlined]
11 devfiler 0x102855ce6 tokio::runtime::task::harness::Harness$LT$T$C$S$GT$::poll_inner::hc3db93efab6897bf + 102 (harness.rs:209) [inlined]
12 devfiler 0x102855ce6 tokio::runtime::task::harness::Harness$LT$T$C$S$GT$::poll::heb064cfaec1bf704 + 118 (harness.rs:154)
13 devfiler 0x1032f768d tokio::runtime::blocking::pool::Inner::run::h2650d2cb3a87b969 + 285
14 devfiler 0x103301dc0 std::sys::backtrace::__rust_begin_short_backtrace::he1ca7edd5a1f80fa + 96
15 devfiler 0x1033035f2 core::ops::function::FnOnce::call_once$u7b$$u7b$vtable.shim$u7d$$u7d$::h5964362f7a142a02 + 226
16 devfiler 0x103340d1b std::sys::pal::unix::thread::Thread::new::thread_start::h110981749b5ebcd9 + 43
17 libsystem_pthread.dylib 0x7ff815beae4d _pthread_start + 115
18 libsystem_pthread.dylib 0x7ff815be6857 thread_start + 15
```

Note that this is not a new issue, it just took me a while to trigger as I almost never use "Top Functions" view.