fix the return value of gettag() to only return the pointer to the provided

tag buffer if the tag was actually found.  There is code that checks to see
if this result is non-zero to determine whether the tag was found or not.
(issue #7092, mikma)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@25060 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -10795,8 +10795,9 @@ static const char *gettag(const struct sip_request *req, char *header, char *tag
 		sep = strchr(tagbuf, ';');
 		if (sep)
 			*sep = '\0';
-	}
 		return tagbuf;
+	}
+	return NULL;
 }
 
 /*! \brief Handle incoming notifications */