Error while fine tuning speaker recognition model
**Describe the bug**

Hi, I am trying to follow the steps underlines here: https://github.com/NVIDIA/NeMo/tree/main/examples/speaker_tasks/recognition
but when i launch : python speaker_reco_finetune.py --pretrained_model='/notebooks/data/atc_tenant/asr/smancha5/Nemo_speaker_training/titanet_l/titanet-l.nemo' --finetune_config_file='titanet-large.yaml' 

It gives me this error:
[NeMo I 2022-06-21 09:06:08 features:200] PADDING: 16
[NeMo I 2022-06-21 09:06:08 label_models:100] loss is Angular Softmax
[NeMo I 2022-06-21 09:06:11 save_restore_connector:243] Model EncDecSpeakerLabelModel was successfully restored from /notebooks/data/atc_tenant/asr/smancha5/Nemo_speaker_training/titanet_l/titanet-l.nemo.
[NeMo I 2022-06-21 09:06:11 label_models:370] Setting up data loaders with manifests provided from model_config
[NeMo I 2022-06-21 09:06:11 collections:290] Filtered duration for loading collection is 0.000000.
[NeMo I 2022-06-21 09:06:11 collections:294] # 16585 files loaded accounting to # 304 labels
[NeMo W 2022-06-21 09:06:11 label_models:133] Total number of 304 found in all the manifest files.
 File "speaker_reco_finetune.py", line 94, in <module>
    main()
  File "speaker_reco_finetune.py", line 79, in main
    speaker_model.setup_finetune_model(finetune_config.model)
  File "/home/smancha5/.local/lib/python3.8/site-packages/nemo/collections/asr/models/label_models.py", line 373, in setup_finetune_model
    self.setup_training_data(model_config.train_ds)
  File "/home/smancha5/.local/lib/python3.8/site-packages/nemo/collections/asr/models/label_models.py", line 201, in setup_training_data
    self._train_dl = self.__setup_dataloader_from_config(config=train_data_layer_config)
  File "/home/smancha5/.local/lib/python3.8/site-packages/nemo/collections/asr/models/label_models.py", line 138, in __setup_dataloader_from_config
    augmentor = process_augmentations(config['augmentor'])
  File "/home/smancha5/.local/lib/python3.8/site-packages/nemo/collections/asr/parts/preprocessing/perturb.py", line 890, in process_augmentations
    augmentation = perturbation_types[augment_name](**augment_kwargs)
  File "/home/smancha5/.local/lib/python3.8/site-packages/nemo/collections/asr/parts/preprocessing/perturb.py", line 403, in __init__
    self._manifest = collections.ASRAudioText(manifest_path, parser=parsers.make_parser([]), index_by_file_id=True)
  File "/home/smancha5/.local/lib/python3.8/site-packages/nemo/collections/common/parts/preprocessing/collections.py", line 214,in __init__
    for item in manifest.item_iter(manifests_files):
  File "/home/smancha5/.local/lib/python3.8/site-packages/nemo/collections/common/parts/preprocessing/manifest.py", line 69, in item_iter
    for manifest_file in manifests_files:
TypeError: 'NoneType' object is not iterable


**Steps/Code to reproduce bug**

python speaker_reco_finetune.py --pretrained_model='/notebooks/data/atc_tenant/asr/smancha5/Nemo_speaker_training/titanet_l/titanet-l.nemo' --finetune_config_file='titanet-large.yaml'  


**Expected behavior**

finetuning of the speaker recog model.

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

 - Environment location: Docker
 - Method of NeMo install:  clone https://github.com/NVIDIA/NeMo.git && cd /NeMo && bash reinstall.sh
 - If method of install is [Docker], provide `docker pull` & `docker run` commands used

**Environment details**

nvcr.io/nvidia/pytorch:22.03-py3
If NVIDIA docker image is used you don't need to specify these.
nvcr.io/nvidia/pytorch:22.03-py3

**Additional context**

Add any other context about the problem here.
Example: GPU model
