[sr-dev] test if $var has been give a value

[Juha Heinanen]

look at this:

	$var(test) = "foo";
	if ($var(test)) {
	  xlog("L_INFO", "EXTR: $var(test) has value\n");
    } else {
	  xlog("L_INFO", "EXTR: $var(test) does NOT have value\n");
    }

	$var(test) = 1;
	if ($var(test)) {
	  xlog("L_INFO", "EXTR: $var(test) has value\n");
    } else {
	  xlog("L_INFO", "EXTR: $var(test) does NOT have value\n");
    }

prints

Sep  2 14:17:23 localhost /usr/sbin/sip-router[14295]: INFO: EXTR: foo does NOT have value
Sep  2 14:17:23 localhost /usr/sbin/sip-router[14295]: INFO: EXTR: 1 has value

this is not good and makes programming VERY error prone.

-- juha