zathurarc not loading if a line contains only spaces
If any line in zathurarc contains only spaces, the config line-by-line loading is immediately stopped with no error message (this could be the reason for similar bugs where the config file is mysteriously not loading). At least this is true for the first line.
It took me quite a while to pinpoint this, I had to recompile in debug mode and use GDB.
Apparently, the culprit is the function g_shell_parse_argv in Glib, which is called from girara in config.c (function config_parse).
It returns false when the line is non-empty and contains spaces. I guess it fails because it expects a valid "argv" string.
As Glib is already a dependency, I would suggest using g_strstrip.