"World" program failing when executing multiple times fast

[fjf2002]

When executing the following program multiple times fast (i. e. press and hold F5):

World w = new World();
new Circle(200, 200, 100);

Chrome reacts with error:

Uncaught TypeError: Cannot read properties of undefined (reading 'renderer')
    at WorldClass.ts:244:23

Firefox reacts with:

Uncaught TypeError: this.app is undefined
    onProgramStopped WorldClass.ts:244
    setTimeout handler*onProgramStopped WorldClass.ts:243
    s WorldClass.ts:174
    fire EventManager.ts:55
    setState Interpreter.ts:400
    run Scheduler.ts:165

[martin-pabst]

Thank you!