Inference with pretrained "stt_en_conformer_ctc_medium" ASR model crashes in python 3.8.10
**Describe the bug**

Inference with the medium model specifically causes an error;
![medium_issue](https://user-images.githubusercontent.com/37636054/191699865-d490f214-6a55-4976-9a77-b2a828f64abe.png)

Works totally fine on the same audio file with the following models;

- stt_en_conformer_ctc_small_ls
- stt_en_conformer_ctc_large
- stt_en_conformer_transducer_large

I've so far only encountered the problem in python 3.8.10. In Google Colab and in Python 3.10.4 it works fine.

**Steps/Code to reproduce bug**

In python 3.8.10, 

installed with;

`nemo_toolkit[all] @ git+https://github.com/NVIDIA/NeMo.git@a4ff215ecc9fafd7127223bc21fd50cf023de592"`

Loaded from local pretrained checkpoint (previously downloaded from NGC)

 
`model = nemo_asr.models.ASRModel.restore_from(restore_path=model_path)`
`model.eval()`
`model.freeze()`
`model.preprocessor.featurizer.dither = 0.0`
`model.preprocessor.featurizer.pad_to = 0`

`decoding_cfg = model.cfg.decoding`
`decoding_cfg.preserve_alignments = True`
`decoding_cfg.compute_timestamps = True`
`model.change_decoding_strategy(decoding_cfg)`
`hypothesis = model.transcribe(paths2audio_files=[audio_path_or_url], return_hypotheses=True)[0]`

**Expected behavior**

Inference should finish without "list index out of range"


**Environment details**

- OS version Ubuntu 20.04
- PyTorch version: 1.12.1
- Python version: 3.8.10

