Added vecty.Nil, prevent replaceNode if new node is nil

dom.go

@@ -247,3 +247,22 @@ func (c *Composite) ReconcileBody() {
 		replaceNode(c.Body.Node(), oldBody.Node())
 	}
 }
+
+type nilComponent struct {
+	node *js.Object
+}
+
+// Apply implements the Markup interface.
+func (s *nilComponent) Apply(element *Element) {}
+
+func (s *nilComponent) Reconcile(oldComp Component) {}
+
+func (s *nilComponent) Node() *js.Object {
+	return nil
+}
+
+func (e *nilComponent) Unmount() {}
+
+func Nil() Component {
+	return &nilComponent{}
+}

domutil.go

@@ -10,5 +10,8 @@ func replaceNode(newNode, oldNode *js.Object) {
 	if newNode == oldNode {
 		return
 	}
+	if newNode == nil {
+		return
+	}
 	oldNode.Get("parentNode").Call("replaceChild", newNode, oldNode)
 }