Huggingface model doesn't convert to ggml

[kabyanil]

I finetuned Whisper-small on a custom dataset. When I try to convert the hf model to ggml using convert-h5-to-ggml.py, I get an error saying max_length is not an integer. Upon reviewing the config.json, I saw that the max_length param was set to null. Setting it to 448 (suggested by line 89 in convert-h5-to-ggml.py file) solved the issue.

Modifying the if block in the script will fix the issue, but sharing the modification of the param in config.json as a quick fix for my fellow devs.

Happy to open a PR to fix this if required.