Song separation lines containing whitespaces

[dib0]

Hi there,

In my church, we often copy song lyrics from Word documents provided by our band. These documents sometimes contain lines that appear blank but actually include whitespace characters (spaces or tabs). As a result, Quelea doesn’t recognize them as empty lines, and lyrics that should be separated into different slides are merged into one.

With this change, any line containing only whitespace is treated as a proper blank line, ensuring that slides are split where the user expects them to be.

I hope this helps other users who encounter the same issue. Thank you for considering my contribution!