fix: entities iterator

app/ecs/ecs.js

@@ -242,28 +242,17 @@ export default class Ecs {
       this.Components[i].destroyMany(destroying[i]);
     }
     for (const entityId of entityIds) {
-      this.$$entities[entityId] = undefined;
+      delete this.$$entities[entityId];
       this.diff[entityId] = false;
     }
   }
 
   get entities() {
-    const it = Object.values(this.$$entities).values();
-    return {
-      [Symbol.iterator]() {
-        return this;
-      },
-      next: () => {
-        let result = it.next();
-        while (!result.done && !result.value) {
-          result = it.next();
+    const ids = [];
+    for (const entity of Object.values(this.$$entities)) {
+      ids.push(entity.id);
     }
-        if (result.done) {
-          return {done: true, value: undefined};
-        }
-        return {done: false, value: result.value.id};
-      },
-    };
+    return ids;
   }
 
   get(entityId) {