fix createFromSnippetAsync for particle

src/Particles/particleHelper.ts

@@ -166,8 +166,10 @@ export class ParticleHelper {
      * @returns a promise that will resolve to the new particle system
      */
     public static CreateFromSnippetAsync(snippetId: string, scene: Scene, gpu: boolean = false, rootUrl: string = ""): Promise<IParticleSystem> {
-        if (snippetId === "_BLANK") {
-            return Promise.resolve(this.CreateDefault(null));
+        if (snippetId === "_BLANK") {        
+            let system = this.CreateDefault(null);
+            system.start();
+            return Promise.resolve(system);
         }
 
         return new Promise((resolve, reject) => {