Old subtitles remain after selecting new subtitles

[v0lt]

After selecting other subtitles, the text of the old subtitles sometimes continues to be displayed until the text of the new subtitles appears.
This can be seen when there are subtitles with and without lyrics.

I give a link to the sample. Start playback, select karaoke subtitles first, and then external subtitles.

[Masaiki]

Known problem, previously felt that the impact is minor so it has been not touched
Will be figured recently.

[Masaiki]

A test build for this

[v0lt]

The test build seems to work correctly.

[Masaiki]

fixed by c9a683b