Fix #62 Catch TypeError when converting string to time

This happens when upgrading from old versions and
we have old sessions that has some old time formats.

Author: kiowa

session_security/utils.py

@@ -34,3 +34,6 @@ def get_last_activity(session):
         #################################################################
 
         return datetime.now()
+    except TypeError:
+        return datetime.now()
+