Question Answering Colab Notebook Error
**Describe the bug**

I get an error when trying to run inference on the provided question answering tutorial notebook.

**Steps/Code to reproduce bug**

Run this notebook to reproduce the error.
https://colab.research.google.com/github/NVIDIA/NeMo/blob/stable/tutorials/nlp/Question_Answering.ipynb

**Expected behavior**

It should run successfully

**Environment overview (please complete the following information)**

 - Environment location: Collab

**Additional context**

Error: `ReferenceError: weakly-referenced object no longer exists`
Code: `exp_dir = exp_manager(model.trainer, config.exp_manager)`