Define the logo CSS class on the field, not on the field group.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@9734 20353a03-c40f-0410-a6d1-a30d3c3de9de

bt5/erp5_web/SkinTemplateItem/portal_skins/erp5_web_default_theme/erp5_web_default_layout/website_logo.xml

@@ -211,7 +211,7 @@
                 </item>
                 <item>
                     <key> <string>css_class</string> </key>
-                    <value> <string></string> </value>
+                    <value> <string>centered logo</string> </value>
                 </item>
                 <item>
                     <key> <string>default</string> </key>