Catching JS error in worker scope from evaluating JS in devtools panics

[jdm]

called `Option::unwrap()` on a `None` value (thread WebWorker for http://localhost:8000/w.js, at components/script/dom/dedicatedworkerglobalscope.rs:502)
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /Users/joshmatthews/.cargo/git/checkouts/backtrace-rs-96ebaf1bcb788384/91a0aa4/src/backtrace/libunwind.rs:86
      backtrace::backtrace::trace_unsynchronized
             at /Users/joshmatthews/.cargo/git/checkouts/backtrace-rs-96ebaf1bcb788384/91a0aa4/src/backtrace/mod.rs:66
   1: <servo::backtrace::Print as core::fmt::Debug>::fmt
             at ports/glutin/backtrace.rs:49
   2: core::fmt::write
             at src/libcore/fmt/mod.rs:1069
   3: std::io::Write::write_fmt
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libstd/io/mod.rs:1504
   4: servo::backtrace::print
             at ports/glutin/backtrace.rs:17
   5: servo::main::{{closure}}
             at ports/glutin/main2.rs:150
   6: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:515
   7: rust_begin_unwind
             at src/libstd/panicking.rs:419
   8: std::panicking::begin_panic
   9: std::panicking::begin_panic
  10: core::option::Option<T>::unwrap
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libcore/macros/mod.rs:34
  11: script::dom::dedicatedworkerglobalscope::DedicatedWorkerGlobalScope::forward_error_to_worker_object
             at components/script/dom/dedicatedworkerglobalscope.rs:502
  12: script::dom::globalscope::GlobalScope::report_an_error
             at components/script/dom/globalscope.rs:2020
  13: script::dom::bindings::error::report_pending_exception
             at components/script/dom/bindings/error.rs:290
  14: script::dom::globalscope::GlobalScope::evaluate_script_on_global_with_result::{{closure}}
             at components/script/dom/globalscope.rs:2176
  15: profile_traits::time::profile
             at /Users/joshmatthews/src/servo-master/components/profile_traits/time.rs:147
  16: script::dom::globalscope::GlobalScope::evaluate_script_on_global_with_result
             at components/script/dom/globalscope.rs:2150
  17: script::dom::globalscope::GlobalScope::evaluate_js_on_global_with_result
             at components/script/dom/globalscope.rs:2129
  18: script::devtools::handle_evaluate_js
             at components/script/devtools.rs:37
  19: script::dom::dedicatedworkerglobalscope::DedicatedWorkerGlobalScope::handle_mixed_message
             at components/script/dom/dedicatedworkerglobalscope.rs:481
  20: <script::dom::dedicatedworkerglobalscope::DedicatedWorkerGlobalScope as script::dom::abstractworkerglobalscope::WorkerEventLoopMethods>::handle_event
             at components/script/dom/dedicatedworkerglobalscope.rs:195
  21: script::dom::abstractworkerglobalscope::run_worker_event_loop
             at components/script/dom/abstractworkerglobalscope.rs:139
  22: script::dom::dedicatedworkerglobalscope::DedicatedWorkerGlobalScope::run_worker_scope::{{closure}}::{{closure}}
             at components/script/dom/dedicatedworkerglobalscope.rs:418
  23: profile_traits::mem::ProfilerChan::run_with_memory_reporting
             at /Users/joshmatthews/src/servo-master/components/profile_traits/mem.rs:88
  24: script::dom::dedicatedworkerglobalscope::DedicatedWorkerGlobalScope::run_worker_scope::{{closure}}
             at components/script/dom/dedicatedworkerglobalscope.rs:407
  25: std::sys_common::backtrace::__rust_begin_short_backtrace
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libstd/sys_common/backtrace.rs:130
  26: std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}}
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libstd/thread/mod.rs:475
  27: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libstd/panic.rs:318
  28: std::panicking::try::do_call
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libstd/panicking.rs:331
  29: __rust_try
  30: std::panicking::try
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libstd/panicking.rs:274
  31: std::panic::catch_unwind
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libstd/panic.rs:394
  32: std::thread::Builder::spawn_unchecked::{{closure}}
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libstd/thread/mod.rs:474
  33: core::ops::function::FnOnce::call_once{{vtable.shim}}
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/libcore/ops/function.rs:232
  34: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/liballoc/boxed.rs:1008
  35: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/liballoc/boxed.rs:1008
      std::sys::unix::thread::Thread::new::thread_start
             at src/libstd/sys/unix/thread.rs:87
  36: <unknown>

[jdm]

The devtools messages don't have the AutoWorkerReset that messages from the script thread do, which is the cause of this panic.

[jdm]

This happens when I evaluate console.log("hi") in the console, but not "hi".