app_stack: protect against missing parameters to STACK_PEEK and LOCAL_PEEK

STACK_PEEK requires 2 parameters and LOCAL_PEEK requires 1 parameter.  This
protects against situations where those parameters are blank or missing by
logging an error and returning.

(closes issue ASTERISK-23220)
Reported by: James Sharp
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Merged revisions 407100 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 407103 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 407104 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@407105 65c4cc65-6c06-0410-ace0-fbb531ad65f3