"empty font directory name ignored" error for previously-valid config

With Fontconfig 2.13.1, we used a config file with a line like this: <dir prefix="xdg"></dir>

This worked fine -- the fonts were loaded from XDG_DATA_HOME, which was set to an appropriate directory in the environment.

With Fontconfig 2.13.92, this line produces the warning "empty font directory name ignored" and the directory is not added. This change was made in cb1df8cb

For backwards compatibility, I would suggest allowing the old behavior. If this functionality is deprecated, the warning should make that clear.

By the way, the following line seems to be parsed just fine in 2.13.92: <cachedir prefix="xdg"></cachedir> If this is also deprecated, I would suggest adding a warning when parsing cachedir as well.

As a workaround, I have modified the offending line to be: <dir prefix="xdg">.</dir> (with a dot as the dir name).