[#2600] Fix Login to add Organization button

Just don't show any button if not authorised to add organisations, same
as with e.g. add dataset etc.

Also fix broken group_create auth function

ckan/logic/auth/publisher/create.py

@@ -79,7 +79,7 @@ def group_create(context, data_dict=None):
     model = context['model']
     user  = context['user']
 
-    if not user:
+    if not model.User.get(user):
         return {'success': False, 'msg': _('User is not authorized to create groups') }
 
     if Authorizer.is_sysadmin(user):

ckanext/organizations/templates/organization_layout.html

@@ -33,12 +33,9 @@
         <li class="${'active' if c.action=='index' else ''}">
           ${h.subnav_named_route(c, h.icon('group') + _('List Organizations'), "organization_index", action="index" )}
         </li>
-        <li style="display:none;" class="ckan-logged-in ${'active' if c.action=='new' else ''}">
+        <li py:if="h.check_access('group_create')" class="${'active' if c.action=='new' else ''}">
           ${ h.subnav_named_route(c, h.icon('group_add') + _('Add an Organization'), "organization_new", action='new')}
         </li>
-        <li class="ckan-logged-out ${'active' if c.action=='new' else ''}">
-          ${h.subnav_link(c, h.icon('group_add') + _('Login to Add an Organization'), controller='group', action='new')}
-        </li>
       </py:otherwise>
     </ul>
   </py:match>