Multiple CSS classes per element don’t work

Hello. First of all, amazing plugin, which I already said in a review. But I encounter an issues while adding more than 1 class per element (screenshot: https://clip2net.com/s/4gb2ze5).
I receive the error “Please match the requested format.” because from what I see the pattern regex doesn’t contain the whitespace. Easy fix for you for the next version and very helpful for the users in some cases.