If the subtitle is empty or all spaces, the rendering fails

[huanghaiyang]

[Script Info] ; //all spaces Synch Point:1 ScriptType:v4.00+ Collisions:Normal PlayResX:1920 PlayResY:1080

[V4+ Styles] Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding Style: Default, roboto lt, 100, &H00FFFFFF, &H00FFFFFF, &H005D5D5D, &H00000000, 0, 0, 0, 0, 100, 100, 0, 0, 1, 3, 0, 2, 72, 72, 85, 134

[Events] Format: Layer, Start, End, Style, Actor, MarginL, MarginR, MarginV, Effect, Text Dialogue: 0,0:00:00.00,0:00:01.00,Default,NTP,0000,0000,0000,,{\c&H00ffffff&}{\3c&H005d5d5d&}{\fs112}{\fnRoboto Lt}{\b0}{\i0}{\u0} \N