more changes, not visible to the end user yet, for spam UI. bug #169638. r/sr=bienvenu

mailnews/base/resources/content/junkMail.js

@@ -160,7 +160,7 @@ function conditionallyEnableUI(id)
     document.getElementById("purgeLabel").disabled = !enabled || !checked;
   }
 
-  if (!id || id == "purge") {
+  if (id == "purge") {
     enabled = document.getElementById("purge").checked;
     document.getElementById("purgeInterval").disabled = !enabled;
     document.getElementById("purgeLabel").disabled = !enabled;

mailnews/base/resources/content/junkMail.xul

@@ -99,7 +99,7 @@
       </grid>
     </radiogroup>
     
-    <hbox autostretch="never">
+    <hbox autostretch="never" align="center">
       <spacer width="20px"/>
       <checkbox id="purge" oncommand="conditionallyEnableUI('purge')" accesskey="&purge1.accesskey;" label="&purge1.label;"/>
       <textbox size="3" id="purgeInterval" />