Fix index error ``list index out of range``, when file is empty.
r? @Wafflespeanut
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] There are tests for these changes
Source-Repo: https://github.com/servo/servo
Source-Revision: c3ce9f2c909cd75c8f424bcef4036d0e29476546
--HG--
rename : servo/python/tidy/servo_tidy_tests/test_ignored/whee/foo/bar.rs => servo/python/tidy/servo_tidy_tests/empty_file.rs
