[chkpt conversion] handle the case where tp=0 , should be 1

[stas00]

This PR is trying to fix:

Traceback (most recent call last): 
 File "/gpfswork/rech/six/commun/code/Megatron-DeepSpeed/tools/convert_checkpoint/deepspeed_to_transformers.py", line 83, in <module> 
   main() 
 File "/gpfswork/rech/six/commun/code/Megatron-DeepSpeed/tools/convert_checkpoint/deepspeed_to_transformers.py", line 22, in main 
   ds_checkpoint = DeepSpeedCheckpoint(args.input_folder, args.target_tp, args.target_pp) 
 File "/gpfsssd/worksf/projects/rech/six/commun/code/Megatron-DeepSpeed/tools/convert_checkpoint/deepspeed_checkpoint.py", line 36, in __init__ 
   self.dp_degree = len(self.zero_files) // (self.original_pp_degree * self.original_tp_degree) 
ZeroDivisionError: integer division or modulo by zero

it seems we have original_pp_degree = 0 rather than 1

[stas00]

@thomasw21, please feel free to close this one or build on top of it, either way works.

I think we should test too that original_pp_degree != 0

[thomasw21]

@stas00 perfect, I'll probably convert all of them to asserts. I've yet to rule out that the checkpoint file is corrupted ...