fix(renderer): stop inserting Placeholders children

Author: sis0k0

nativescript-angular/renderer.ts

@@ -88,7 +88,10 @@ export class NativeScriptRenderer extends RendererV2 {
 
     appendChild(parent: any, newChild: NgView): void {
         traceLog(`NativeScriptRenderer.appendChild child: ${newChild} parent: ${parent}`);
-        this.viewUtil.insertChild(parent, newChild);
+
+        if (parent) {
+            this.viewUtil.insertChild(parent, newChild);
+        }
     }
 
     insertBefore(parent: NgView, newChild: NgView, refChildIndex: number): void {
@@ -199,7 +202,7 @@ export class NativeScriptRenderer extends RendererV2 {
         return this.viewUtil.createView(name);
     }
 
-    createText(_value: string): NgView {
+    createText(_value: string) {
         traceLog("NativeScriptRenderer.createText");
         return this.viewUtil.createText();
     }

nativescript-angular/view-util.ts

@@ -22,6 +22,7 @@ export type ViewExtensions = ViewExtensions;
 export type NgView = NgView;
 export type NgLayoutBase = LayoutBase & ViewExtensions;
 export type NgContentView = ContentView & ViewExtensions;
+export type NgPlaceholder = Placeholder & ViewExtensions;
 export type BeforeAttachAction = (view: View) => void;
 
 export function isView(view: any): view is NgView {
@@ -36,6 +37,10 @@ export function isContentView(view: any): view is NgContentView {
     return view instanceof ContentView;
 }
 
+export function isPlaceholder(view: any): view is NgPlaceholder {
+    return view instanceof Placeholder;
+}
+
 const propertyMaps: Map<Function, Map<string, string>> = new Map<Function, Map<string, string>>();
 
 export class ViewUtil {
@@ -48,7 +53,7 @@ export class ViewUtil {
     }
 
     public insertChild(parent: any, child: NgView, atIndex: number = -1) {
-        if (!parent || child.meta.skipAddToDom) {
+        if (!parent || child.meta.skipAddToDom || isPlaceholder(child) === true) {
             return;
         }