Added meta where and jquery observe field. Fixed members view.

app/models/membership.rb

@@ -2,12 +2,16 @@ class Membership < ActiveRecord::Base
   
   belongs_to :user
   belongs_to :group
+
+  before_destroy :check_last_admin
   
   # messages
   ERR_NO_ADMIN_MEMBER_DELETE = "Mitgliedschaft kann nicht beendet werden. Du bist die letzte Administratorin"
-  
+
+  protected
+
   # check if this is the last admin-membership and deny
-  def before_destroy
+  def check_last_admin
     raise ERR_NO_ADMIN_MEMBER_DELETE if self.group.role_admin? && self.group.memberships.size == 1 && Group.find_all_by_role_admin(true).size == 1 
   end
 end