DCP-o-matic 2.18.13 released

[carl]

Download it now from here.

• Fix insertion of incorrect black frames when raising frame rate by a lot (#2993).
• Fix font error when finding missing files in a project that contains subtitles.
• Allow configuration of Grok from the command line client (#2981).
• Allow start of DCP encode job after pausing export.
• Tolerate filesystem errors when looking for DCPs to verify (#2982).