Add additional error checks

mocha_server.py

@@ -135,9 +135,9 @@ def process_request(uri):
 
     if len(parts) < 2:
         output = None
-    elif parts[1] == 'users':
+    elif parts[1] == 'users' and len(parts) > 2:
         output = fetch_user(parts[2])
-    elif parts[1] == 'top':
+    elif parts[1] == 'top' and len(parts) > 2:
         output = fetch_top_n(parts[2])
     else:
         output = None