Cancel button when opening file without FPS

[chenlung]

When prompted to select an FPS upon import (e.g. a millisecond-based file, such as a WebVTT): if Cancel is clicked, it will use whatever has been set as the default (the General tab within Settings).

I propose that Cancel be removed or renamed to 'Use default'.

Using Tero Subtitler 1.0.1.0, Mac 10.11.6.

[chenlung]

Fixed for 1.0.1.5.