Summary widget unsubscribe (#2364)

* Delete subscription handle to prevent double unsubscribe error

* Do not attempt to render undefined telemetry datum

src/plugins/summaryWidget/src/ConditionManager.js

@@ -237,6 +237,7 @@ define ([
         });
         delete this.compositionObjs[objectId];
         this.subscriptions[objectId](); //unsubscribe from telemetry source
+        delete this.subscriptions[objectId];
         this.eventEmitter.emit('remove', identifier);
 
         if (_.isEmpty(this.compositionObjs)) {

src/plugins/summaryWidget/src/telemetry/SummaryWidgetTelemetryProvider.js

@@ -43,7 +43,7 @@ define([
         return evaluator.requestLatest(options)
             .then(function (latestDatum) {
                 this.pool.release(evaluator);
-                return [latestDatum];
+                return latestDatum ? [latestDatum] : [];
             }.bind(this));
     };
 

src/plugins/summaryWidget/src/views/SummaryWidgetView.js

@@ -52,7 +52,10 @@ define([
             strategy: 'latest',
             size: 1
         }).then(function (results) {
-            if (this.destroyed || this.hasUpdated || this.renderTracker !== renderTracker) {
+            if (this.destroyed ||
+                this.hasUpdated ||
+                this.renderTracker !== renderTracker ||
+                results.length === 0) {
                 return;
             }
             this.updateState(results[results.length - 1]);