Only lookup and delete the monitor wait data if it was allocated.

tests/standalone/standalone.status

 # Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 package/invalid_uri_test: Fail, OK # Fails intentionally
 
 [ $runtime == vm && ( $system == windows ) ]
 io/raw_socket_test: Pass, Fail # Issue 8901
 io/http_shutdown_test: Pass, Fail # Issue  9101
 
 [ $runtime == vm ]
 package/package_isolate_test: Fail # http://dartbug.com/7520.
 io/raw_server_socket_cancel_test: Pass, Fail, Timeout # Issue 8675
 
 # Fails with a connection refused error on the buildbot.
 # Issue 8232.
 debugger/basic_debugger_test: Skip
 
 [ $runtime == vm && $checked ]
 # These tests have type errors on purpose.
 io/process_invalid_arguments_test: Fail, OK
 io/directory_invalid_arguments_test: Fail, OK
 io/file_invalid_arguments_test: Fail, OK
 io/socket_invalid_arguments_test: Fail, OK
 io/stdout_bad_argument_test: Fail, OK
 # These test have type errors on purpose and take very long to run in
 # checked mode with no benefit. Skip.
 io/file_fuzz_test: Skip
 io/directory_fuzz_test: Skip
-io/process_exit_negative_test: Pass, Crash # Issue 9403
 
 [ $runtime == vm && $system == macos ]
 io/regress_7191_test: Pass, Timeout # http://dartbug.com/8091
 
 # This test fails with "Too many open files" on the Mac OS buildbot.
 # This is expected as MacOS by default runs with a very low number
 # of allowed open files ('ulimit -n' says something like 256).
 io/socket_many_connections_test: Skip
 
 # These tests pass on MacOS 10.8.2 but fails on the buildbot machines
@@ skipping 83 matching lines @@
 *: Skip
 
 [ $arch == simarm ]
 *: Skip
 
 [ $arch == mips ]
 *: Skip
 
 [ $arch == simmips ]
 *: Skip