[#1725] Fix exception caught when there's no CKAN_CURRENT_URL

When we try to get a key from a dict and it doesn't exist, a KeyError is
raised, not a TypeError.

ckanext/datastore/db.py

@@ -847,7 +847,7 @@ def _insert_links(data_dict, limit, offset):
     # get the url from the request
     try:
         urlstring = toolkit.request.environ['CKAN_CURRENT_URL']
-    except TypeError:
+    except KeyError:
         return  # no links required for local actions
 
     # change the offset in the url