Fix device summary when state not fully formed

appengine/swarming/ui/res/imp/botpage/device-summary.html

Index: appengine/swarming/ui/res/imp/botpage/device-summary.html
diff --git a/appengine/swarming/ui/res/imp/botpage/device-summary.html b/appengine/swarming/ui/res/imp/botpage/device-summary.html
index 3725c51747ca3ab10ffa4cee6f547bbc56c93449..0e606f7db029e93a91c94ba53d01e360493c8218 100644
--- a/appengine/swarming/ui/res/imp/botpage/device-summary.html
+++ b/appengine/swarming/ui/res/imp/botpage/device-summary.html
@@ -101,11 +101,12 @@
             var d = this.state.devices[id];
             var device = {
               id: id,
-              battery: d.battery.level,
-              state: d.state,
+              state: d.state || "???",
             };
+            device.battery = (d.battery && d.battery.level) || "???"
             var count = 0;
             var totalTemp = 0;
+            d.temp = d.temp || [];
             for (var t in d.temp) {
               totalTemp += parseFloat(d.temp[t]);
               count++;
@@ -113,6 +114,8 @@
             // Report the average temperature of all sensors.
             if (count) {
               device.temp = (totalTemp/count).toFixed(1);
+            } else {
+              device.temp == "???";
             }
             arr.push(device);
           }