erp5_web_blog: check effective date firstly

bt5/erp5_web_blog/SkinTemplateItem/portal_skins/erp5_web_blog/WebSection_viewBlogFrontPage/listbox.xml

@@ -179,6 +179,10 @@
                     <key> <string>sort</string> </key>
                     <value>
                       <list>
+                        <tuple>
+                          <string>effective_date</string>
+                          <string>descending</string>
+                        </tuple>
                         <tuple>
                           <string>creation_date</string>
                           <string>descending</string>

bt5/erp5_web_blog/SkinTemplateItem/portal_skins/erp5_web_blog/WebSection_viewBlogFrontPage/listbox_effective_date.xml

@@ -109,7 +109,7 @@
       <dictionary>
         <item>
             <key> <string>_text</string> </key>
-            <value> <string>python: cell.getCreationDate()</string> </value>
+            <value> <string>python: cell.getEffectiveDate() if cell.getEffectiveDate() else cell.getCreationDate()</string> </value>
         </item>
       </dictionary>
     </pickle>