Bug 341872: Download manager leaks helperApps, patch by Regis Caspar <regis.caspar+bz@gmail.com>, r=me

toolkit/mozapps/downloads/content/unknownContentType.xul

@@ -50,7 +50,7 @@
 
 <dialog id="unknownContentType"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
-        onload="dialog.initDialog();" onunload="if (dialog) dialog.onCancel();"
+        onload="dialog.initDialog();" onunload="this.HelperApps = null; if (dialog) dialog.onCancel();"
         onblur="if (dialog) dialog.onBlur(event);" onfocus="dialog.onFocus(event);"
         style="width: 34em;"
         screenX="" screenY=""