Fixed optimization label

doc/advanced/optimization.txt

-
-.. _optimization:
-
-============
-Optimization
-============
-
-WRITEME
-
-.. _navigator:
-
-Navigator
-=========
-
-WRITEME

doc/advanced_tutorial/optimization.txt

 
+.. _optimization:
 
 ==================
 Graph optimization

doc/indexes/index.txt

@@ -4,7 +4,7 @@ Indexes
 =======
 
 The following indexes are generated automatically and cover most
-:ref:`Ops <op>`, :ref:`Types <type>` and :ref:`Optimizers <optimizer>`
+:ref:`Ops <op>`, :ref:`Types <type>` and :ref:`Optimizers <optimization>`
 in Theano.
 
 .. toctree::