This changeset ensures the result of the font URL functions is a `string` before using it in `add_editor_style()`, to avoid PHP warnings on child themes. This similarily updates Twenty Thirteen, Twenty Fourteen, Twenty Fifteen, Twenty Sixteen, and Twenty Seventeen.
Props jordesign, SergeyBiryukov, sabernhardt, huzaifaalmesbah, shailu25.
Fixes#59704.
Built from https://develop.svn.wordpress.org/trunk@57601
git-svn-id: http://core.svn.wordpress.org/trunk@57102 1a063a9b-81f0-0310-95a4-ce76da25c4cd