Fix .m2ts video timecodes

Commit [b7d228c](https://github.com/arch1t3cht/Aegisub/commit/b7d228c0ced1726b1129f385fe31c47a55b6ee44) breaks .m2ts Blu-ray videos. Every video in a Blu-ray I checked has frame 0 at 1:10:00.000, including one video that is under 1 minute long.