Fixed latest resource for collection

Closes #67

ckanext/odsh/collection/helpers.py

@@ -174,5 +174,7 @@ def get_latest_resources_for_format(collection_name, resource_format):
     if not resources:
         return None
     resources_with_asked_type = [r for r in resources if r.get('format').upper() == resource_format.upper()]
+    if not resources_with_asked_type:
+      return None
     resources_sorted = sorted(resources_with_asked_type, key=itemgetter('id','created'), reverse=True)
     return resources_sorted[-1]

ckanext/odsh/collection/plugin.py

@@ -57,7 +57,7 @@ class CollectionsPlugin(plugins.SingletonPlugin, DefaultDatasetForm):
         url_type = latest_resources.get('url_type')
         if url_type is None:
             resource_url = latest_resources.get('url')
-            toolkit.redirect_to(resource_url)
+            return toolkit.redirect_to(resource_url)
         if url_type == 'upload':
             download_package_id = latest_resources.get('package_id')
             download_resource_id = latest_resources.get('id')