fix expires

kamailio/registrar-role.cfg

@@ -107,13 +107,14 @@ route[ATTEMPT_AUTHORIZATION]
     consume_credentials();
     save("location");
 
-    $var(expires) = @contact.expires;
-    if($var(expires) == $null) {
-        $var(expires) = $hdr(Expires);
-    }
-
-    if($var(expires) == $null) {
-        $var(expires) = REGISTRAR_MIN_EXPIRES;
+    if(@contact.expires) {
+        $var(expires) = @contact.expires;
+    } else { 
+        if($hdr(Expires)) {
+           $var(expires) = $hdr(Expires);
+        } else {
+           $var(expires) = REGISTRAR_MIN_EXPIRES;
+        }
     }
 
     if($var(expires) == 0) {