Added missing cast (#9342)

Change-Id: If8078ffea6fd2bcaf62591ed8930905cdc1d3a1d

server/src/com/vaadin/ui/Component.java

@@ -753,7 +753,7 @@ public interface Component extends ClientConnector, Sizeable, Serializable {
          * @return the source component of the event
          */
         public Component getComponent() {
-            return getSource();
+            return (Component) getSource();
         }
 
     }