final tiny touch ups

src/main/java/ch/unibas/dmi/dbis/cs108/multiplayer/client/gui/chat/NodeWithChildren.java

@@ -9,7 +9,9 @@ public interface NodeWithChildren {
 
   void create();
 
-  public default Node getChildren(){};
+  public default Node getChildren() {
+    return null;
+  }
 
   void createNodeHierarchy();
 }

src/main/java/ch/unibas/dmi/dbis/cs108/multiplayer/client/gui/chat/OutMsgTargetChooserNode.java

@@ -19,7 +19,7 @@ public class OutMsgTargetChooserNode extends ToggleGroup implements NodeWithChil
 
   @Override
   public Node getChildren() {
-    NodeWithChildren.super.getChildren();
+    return NodeWithChildren.super.getChildren();
   }
 
   @Override