Fix typing issues in engine.ts

[creadicted]

In the engine.ts file are two methods - abort() and lock() that lead to errors:

public async abort() {
    return new Promise((ret) => {
      if (this.state === State.PROCESSED) {
        this.state = State.ABORT;
        this.onAbort = ret;
      } else if (this.state === State.ABORT) {
        this.onAbort();
        this.onAbort = ret;
      } else ret();
    });
  }

 private async lock(node: EngineNode) {
    return new Promise((res) => {
      node.unlockPool = node.unlockPool || [];
      if (node.busy && !node.outputData) node.unlockPool.push(res);
      else res();

      node.busy = true;
    });
  }

They both handle the Promise execution in a way that is not familiar to me, so I need to investigate. But I also do not want to forget it - thats the reason why I created this issue.