Gemfile: update rbpdf version to 1.18.1 (#17570)

git-svn-id: http://svn.redmine.org/redmine@13409 e93f8b46-1217-0410-a6f0-8f06a7374b81
remove trailing white-space from app/models/issue_custom_field.rb

git-svn-id: http://svn.redmine.org/redmine@13410 e93f8b46-1217-0410-a6f0-8f06a7374b81