refactor: out of closure

packages/physics/traits/emitter.trait.js

@@ -161,11 +161,11 @@ export class Emitter extends decorate(Trait) {
       },
 
       emitParticleJson: (json) => {
-        return K.stream((emitter) => {
         let {
           count = 1,
           rate = 0,
         } = json;
+        const stream = K.stream((emitter) => {
           if (0 === rate) {
             for (let i = 0; i < count; ++i) {
               this.emitParticleJson(json, emitter);