handle case when the topic is not published

src/VideoStream/index.js

@@ -6,9 +6,19 @@ class VideoStream extends Component {
         super(props)
 
         const hasUrl = ('url' in this.props && this.props.url);
+        this.topic = '/pepper/image_raw';
+        this.defaultImage = '';
+
         this.state = {
-            url: hasUrl ? this.props.url : 'http://localhost:8081/stream?topic=/pepper/image_raw'
+            url: hasUrl ? this.props.url : this.defaultImage
+        };
+
+        this.props.ros.getTopics(function(infos){
+            console.debug(infos.topics)
+            if (undefined !== infos.topics.find(elem => elem === this.topic)) {
+                this.setState({url: 'http://localhost:8081/stream?topic=' + this.topic});
             }
+          }.bind(this))
     }
 
     handleSettingsChange(event) {