check_gn_headers sometimes fails when compilation is skipped. Examples:

https://luci-milo.appspot.com/buildbot/tryserver.chromium.linux/linux_chromium_rel_ng/480369
https://luci-milo.appspot.com/buildbot/tryserver.chromium.linux/linux_chromium_rel_ng/480409
https://luci-milo.appspot.com/buildbot/tryserver.chromium.linux/linux_chromium_rel_ng/480400

All of them have:
analyze
No compile necessary


Error messages:

Running ['/usr/bin/python', '/b/c/b/linux/src/build/check_gn_headers.py', '--out-dir', u'/b/c/b/linux/src/out/Release', '--whitelist', '/b/c/b/linux/src/build/check_gn_headers_whitelist.txt', '--json', '/tmp/tmpiOItRo', '--verbose'] in '/b/c/b/linux/src' (env: None)
Traceback (most recent call last):
  File "/b/c/b/linux/src/build/check_gn_headers.py", line 301, in <module>
    sys.exit(main())
  File "/b/c/b/linux/src/build/check_gn_headers.py", line 205, in main
    if not args.skip_dirty_check and not IsBuildClean(args.out_dir):
  File "/b/c/b/linux/src/build/check_gn_headers.py", line 151, in IsBuildClean
    out = subprocess.check_output(cmd)
  File "/usr/lib/python2.7/subprocess.py", line 573, in check_output
    raise CalledProcessError(retcode, cmd, output=output)
subprocess.CalledProcessError: Command '['/b/c/b/linux/src/third_party/depot_tools/ninja', '-C', '/b/c/b/linux/src/out/Release', '-n']' returned non-zero exit status -11
Command ['/usr/bin/python', '/b/c/b/linux/src/build/check_gn_headers.py', '--out-dir', u'/b/c/b/linux/src/out/Release', '--whitelist', '/b/c/b/linux/src/build/check_gn_headers_whitelist.txt', '--json', '/tmp/tmpiOItRo', '--verbose'] returned exit code 1
Traceback (most recent call last):
  File "/b/c/b/linux/src/testing/scripts/check_gn_headers.py", line 47, in <module>
    sys.exit(common.run_script(sys.argv[1:], funcs))
  File "/b/c/b/linux/src/testing/scripts/common.py", line 66, in run_script
    return args.func(args)
  File "/b/c/b/linux/src/testing/scripts/check_gn_headers.py", line 28, in main_run
    failures = json.load(f)
  File "/usr/lib/python2.7/json/__init__.py", line 290, in load
    **kw)
  File "/usr/lib/python2.7/json/__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 366, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python2.7/json/decoder.py", line 384, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded