Fix device summary when state not fully formed

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

 <!--
   This in an HTML Import-able file that contains the definition
   of the following elements:
 
     <device-summary>
 
   Usage:
 
     <device-summary></device-summary>
 
@@ skipping 83 matching lines @@
       _getDevices() {
         var arr = [];
         if (!this.state || !this.state.devices) {
           return arr;
         }
         for (var id in this.state.devices) {
           if (this.state.devices.hasOwnProperty(id)) {
             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++;
             }
             // Report the average temperature of all sensors.
             if (count) {
               device.temp = (totalTemp/count).toFixed(1);
+            } else {
+              device.temp == "???";
             }
             arr.push(device);
           }
         }
         return arr;
       }
     });
   </script>
 </dom-module>