(PUP-10997) ignore empty lines in /etc/group

Author: golflimaechoecho

lib/puppet/provider/user/useradd.rb

@@ -135,7 +135,7 @@ def localgroups
 
     Puppet::FileSystem.each_line(group_file) do |line|
       data = line.chomp.split(':')
-      if data.last.split(',').include?(user)
+      if !data.empty? && data.last.split(',').include?(user)
         @groups_of[user] << data.first
       end
     end