From 60d8e30ecdf7ab3c02fa21d5d16d8490f60b7e3f Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Sat, 11 Jun 2016 16:48:58 -0600
Subject: [PATCH] scanwidget: value may be None

---
 artiq/gui/scanwidget.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/artiq/gui/scanwidget.py b/artiq/gui/scanwidget.py
index 6e8bb240b..de08a8d1d 100644
--- a/artiq/gui/scanwidget.py
+++ b/artiq/gui/scanwidget.py
@@ -71,6 +71,8 @@ class ScanWidget(QtWidgets.QWidget):
         self._setView(left, scale)
 
     def _clamp(self, v):
+        if v is None:
+            return None
         if self._min is not None:
             v = max(self._min, v)
         if self._max is not None: