fix(desktop_picker): Use defaultProps

react/features/desktop-picker/components/DesktopPicker.js

  * @extends Component
  */
 class DesktopPicker extends Component {
+    /**
+     * Default values for DesktopPicker component's properties.
+     *
+     * @static
+     */
+    static defaultProps = {
+        options: {}
+    };
+
     /**
      * DesktopPicker component's property types.
      *
      * @inheritdoc
      */
     componentWillMount() {
-        const options = this.props.options || {};
+        const { desktopSharingSources } = this.props.options;
 
         this._onSourceTypesConfigChanged(
-            options.desktopSharingSources);
+            desktopSharingSources);
         this._updateSources();
         this._startPolling();
     }
             });
         }
 
-        const options = this.props.options || {};
+        const { desktopSharingSources } = this.props.options;
 
         this._onSourceTypesConfigChanged(
-            options.desktopSharingSources);
+            desktopSharingSources);
     }
 
     /**