RTS: Fix outline size when using default style for ASS subtitles.

Fixes #3701
RTS: Add some rounding to ensure higher precision.
RTS: Preserve proper subtitle positioning and constant font size for default style override along different subtitle files.

Fixes #1574
RTS: Don't remove subtitles effect when default style is applied.

"Default Style" option is to apply default style for subtitles and not
actually completely break them.

Fixes #4171
ISR: Don't set subtitle again when manipulating style.

Fixes #2244
ISR: Disable "Default Style" menu item when not applicable.
Set the execute permissions on .bat and .sh files.

Command used to prepare this patch
`git ls-files -z '*.bat' '.sh' | xargs -0 git update-index --chmod=+x`
Avoid dereference of null pointer.

This is highly unlikely.

Fixes CID 1192558