Intermittent crash in /_mozilla/css/position_relative_top_percentage_a.html

[wafflespeanut]

  ▶ CRASH [expected PASS] /_mozilla/css/position_relative_top_percentage_a.html
  │ 
  │ Shutting down the Constellation after generating an output file or exit flag specified
  │ Shutting down the Constellation after generating an output file or exit flag specified
  │ thread 'ScriptThread PipelineId { namespace_id: PipelineNamespaceId(0), index: PipelineIndex(0) }' panicked at 'index out of bounds: the len is 0 but the index is 0', ../src/libcollections/vec.rs:1167
  │ stack backtrace:
  │    1:        0x10c59696b - std::sys::backtrace::tracing::imp::write::h6528da8103c51ab9
  │    2:        0x10c59ceda - std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::hbe741a5cc3c49508
  │    3:        0x10c59caea - std::panicking::default_hook::he0146e6a74621cb4
  │    4:        0x10c3756af - util::panicking::initiate_panic_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::ha2bd86c312dc8d7a
  │    5:        0x10c5846b4 - std::panicking::rust_panic_with_hook::h983af77c1a2e581b
  │    6:        0x10c59d4b6 - std::panicking::begin_panic::he426e15a3766089a
  │    7:        0x10c585cf8 - std::panicking::begin_panic_fmt::hdddb415186c241e7
  │    8:        0x10c59d10f - rust_begin_unwind
  │    9:        0x10c5c3f90 - core::panicking::panic_fmt::hf4e16cb7f0d41a25
  │   10:        0x10c5c4110 - core::panicking::panic_bounds_check::h14f942e6ac026712
  │   11:        0x10b2af3fe - script::dom::browsingcontext::BrowsingContext::active_document::h226f24d08ec44427
  │   12:        0x10b2b411a - script::dom::browsingcontext::BrowsingContext::active_window::h2ba128d21d9d19cf
  │   13:        0x10b8c7a4c - _<script..script_thread..ScriptMemoryFailsafe<'a> as core..ops..Drop>::drop::h299131f5d9bc5b1b
  │   14:        0x10b8cbd2e - std::panicking::try::call::hb8565a24f25031fc
  │   15:        0x10c5a019b - __rust_try
  │   16:        0x10c5a0135 - __rust_maybe_catch_panic
  │   17:        0x10b8cc4f4 - _<F as alloc..boxed..FnBox<A>>::call_box::h78c73797281bb868
  │   18:        0x10c59bc18 - std::sys::thread::Thread::new::thread_start::h9c883b6d445ece46
  │   19:     0x7fff88bee059 - _pthread_body
  │   20:     0x7fff88bedfd6 - _pthread_start
  └ thread panicked while panicking. aborting.

[jdm]

Same as #11671 and #11400.