Break out of 'mfpub' if 'gh-pages' checkout fails

buildroot/share/git/mfpub

 git clean -d -f
 
 # Copy built-site into the gh-pages branch
-git checkout gh-pages
+git checkout gh-pages || { echo "Something went wrong!"; exit 1; }
 rsync -av ${TMPFOLDER}/ ./
 
 # Commit and push the new live site directly