slapos_cloud: Check if the user has permisson before provide a URL

  Only get the product image if the user has access to it.

master/bt5/slapos_cloud/SkinTemplateItem/portal_skins/slapos_cloud/InstanceTree_getDefaultImageAbsoluteUrl.py

 portal = context.getPortalObject()
 url_string = context.getUrlString()
-# set default value of image_url to the panel's logo 
+# set default value of image_url to the panel's logo
 image_url = "gadget_slapos_panel.png"
 
 release = portal.portal_catalog.getResultValue(
@@ -8,7 +8,9 @@ release = portal.portal_catalog.getResultValue(
     url_string=url_string,
 )
 if release is not None:
-  software_product = release.getAggregateValue()
-  image_url = software_product.getDefaultImageAbsoluteUrl()
+  software_product = release.getAggregateValue(
+    checked_permission='Access contents information')
+  if software_product is not None:
+    image_url = software_product.getDefaultImageAbsoluteUrl()
 
 return image_url