indentation based folding: ignore empty lines without any non spaces, fixes crash
indentation based folding: ignore empty lines without any non spaces, fixes crash

svn path=/trunk/kdelibs/kate/; revision=275157

hlamer/kate,hlamer/kate,sandsmark/kate,cmacq2/kate,hlamer/kate,hlamer/kate,sandsmark/kate,sandsmark/kate,hlamer/kate,hlamer/kate,jfmcarreira/kate,DickJ/kate,hlamer/kate,cmacq2/kate,DickJ/kate,sandsmark/kate,jfmcarreira/kate,jfmcarreira/kate,DickJ/kate,hlamer/kate,hlamer/kate,DickJ/kate,cmacq2/kate,hlamer/kate