Bug 1633233

I see the same problem with even a primitive CSS file:

$ dnf list csstidy
Last metadata expiration check: 4:13:35 ago on 2019-01-15T08:55:27 CET.
Installed Packages
csstidy.x86_64                        1.4-20.fc29                        @fedora

$ csstidy

Usage:

csstidy input_filename [
 --allow_html_in_templates=[false|true] |
 --compress_colors=[true|false] |
 --compress_font-weight=[true|false] |
 --discard_invalid_properties=[false|true] |
 --lowercase_s=[false|true] |
 --preserve_css=[false|true] |
 --remove_bslash=[true|false] |
 --remove_last_;=[false|true] |
 --silent=[false|true] |
 --sort_properties=[false|true] |
 --sort_selectors=[false|true] |
 --timestamp=[false|true] |
 --merge_selectors=[2|1|0] |
 --case_properties=[0|1|2] |
 --optimise_shorthands=[1|2|0] |
 --template=[default|filename|low|high|highest] |
 output_filename ]*

$ cat dummy.css 
body {
}

$ csstidy dummy.css 
/usr/include/c++/8/bits/basic_string.h:1048: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::reference std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator[](std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::reference = char&; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type = long unsigned int]: Assertion '__pos <= size()' failed.
Aborted (core dumped)

Created attachment 1520750 [details]
Simple CSS file to cause core dump

There's a similar report for grub-customizer (ticket 1570260). I don't know if the fix from there would be applicable for csstidy.

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