fix exception message in report seachr

when we get to the raise statement, `r` is `None`, so displaying it in the
exception message is useless. `name` is what we want to show.

openerp/addons/base/ir/ir_actions.py

@@ -128,7 +128,7 @@ class ir_actions_report_xml(osv.osv):
                 else:
                     raise Exception, "Unhandled report type: %s" % r
             else:
-                raise Exception, "Required report does not exist: %s" % r
+                raise Exception, "Required report does not exist: %s" % name
 
         return new_report