Use correct state bitmap when creating image list

Regression of 2a0719818a.

src/msw/anybutton.cpp

@@ -420,7 +420,7 @@ private:
                     stateBitmap = bitmap;
             }
 
-            m_iml.Add(bitmap);
+            m_iml.Add(stateBitmap);
         }
 
         // In addition to the states supported by wxWidgets such as normal,