Don't break if bundler is not installed (#6377)
Don't break if bundler is not installed (#6377)

Merge pull request 6377
tillgrallert/jekyll,Strangehill/jekyll,tillgrallert/jekyll,x-way/jekyll,tillgrallert/jekyll,gencer/jekyll,x-way/jekyll,Strangehill/jekyll,yhironaka/yhironaka.github.io,jekyll/jekyll,Strangehill/jekyll,getandpost/jekyll.github.io,gencer/jekyll,jaybe-jekyll/jekyll,ryanshaw/jekyll,chrisfinazzo/jekyll,jaybe-jekyll/jekyll,jekyll/jekyll,fulldecent/jekyll,fulldecent/jekyll,ryanshaw/jekyll,chrisfinazzo/jekyll,Strangehill/jekyll,jaybe-jekyll/jekyll,chrisfinazzo/jekyll,Strangehill/jekyll,ryanshaw/jekyll,jaybe-jekyll/jekyll,tillgrallert/jekyll,ryanshaw/jekyll,jekyll/jekyll,getandpost/jekyll.github.io,fulldecent/jekyll,tillgrallert/jekyll,fulldecent/jekyll,jekyll/jekyll,x-way/jekyll,chrisfinazzo/jekyll,getandpost/jekyll.github.io,x-way/jekyll,gencer/jekyll,gencer/jekyll,gencer/jekyll