Fix a segmentation fault when using an extension with CID matching and no CID.

Attempting to call an extension which used Caller ID matching with a channel that
has an empty caller id string would result in a segmentation fault.

(closes issue ASTERISK-18392
Reported By: Ales Zelenik
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Merged revisions 344608 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 344609 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@344610 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/pbx.c

@@ -2614,7 +2614,7 @@ static int extension_match_core(const char *pattern, const char *data, enum ext_
 		prof_id = ast_add_profile("ext_match", 0);
 	}
 	ast_mark(prof_id, 1);
-	i = _extension_match_core(pattern, data, mode);
+	i = _extension_match_core(ast_strlen_zero(pattern) ? "" : pattern, ast_strlen_zero(data) ? "" : data, mode);
 	ast_mark(prof_id, 0);
 	return i;
 }