Initialize data on the stack so that Park doesn't interpret random arguments.

passdata was only being set in pbx_substitue_variables when arguments were
passed.

(closes issue #16406)
(closes issue #16586)
Reported by: DLNoah
Patches: 
      bug16586v2.patch uploaded by jpeeler (license 325)
Tested by: DLNoah



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@241366 65c4cc65-6c06-0410-ace0-fbb531ad65f3