Intermittent failure in css21_dev/html4/reference/margin-bottom-019-ref.htm

[jdm]

 9:34.58 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) Full command: /Users/servo/buildbot/slave/mac3/build/target/release/servo --cpu --hard-fail --exit -u Servo/wptrunner -Z disable-text-aa --output=/var/folders/16/h7h_cw7d42gbp2bphlppgf_h0000gp/T/tmpBzaiMp/626695b5-9f87-47de-bfb5-42149d379dbb http://localhost:8000/css21_dev/html4/reference/margin-bottom-019-ref.htm --user-stylesheet /Users/servo/buildbot/slave/mac3/build/resources/ahem.css
(pid:58649) "thread 'Constellation' panicked at 'Attempted to construct an Id from a null pointer', /Users/servo/.cargo/registry/src/github.com-0a35038f75765ae4/objc_id-0.0.1/src/id.rs:66"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "stack backtrace:"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "   1:        0x102ff1590 - sys::backtrace::write::h095d0f07f92e7e3eYts"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "   2:        0x102ff4963 - panicking::on_panic::h5f4115f30a6b4860Z7w"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "   3:        0x102fe3922 - rt::unwind::begin_unwind_inner::h7c54671eea5e313e0Cw"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "   4:        0x101ecaf92 - rt::unwind::begin_unwind::h8163611068463542263"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "   5:        0x101ecaf4d - osx_clipboard::ClipboardContext::new::h81ed5eda8feef64a4aa"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "   6:        0x101ccce68 - constellation::Constellation<LTF, STF>::start::closure.18766"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "   7:        0x101ccc908 - boxed::F.FnBox<A>::call_box::h1414755759592328252"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "   8:        0x101ccc202 - rt::unwind::try::try_fn::h9015836644619302537"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "   9:        0x102ff4338 - __rust_try"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "  10:        0x102feff90 - rt::unwind::try::inner_try::h39d984f71e9cc780Tyw"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "  11:        0x101ccc3b7 - boxed::F.FnBox<A>::call_box::h1389811629103310001"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "  12:        0x102ff362d - sys::thread::Thread::new::thread_start::h999b3790b6d4b23deXv"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "  13:     0x7fff8cbf6267 - _pthread_body"
 9:34.59 PROCESS_OUTPUT: Thread-TestrunnerManager-8 (pid:58649) "  14:     0x7fff8cbf61e4 - _pthread_start"

[jdm]

@aweinstock314 This looks related to the recent clipboard integration.

[jdm]

This should no longer occur.