`'NoneType' object has no attribute 'lstrip'` when trying to add a new package

[lolmaus]

Trying to add a package from this URL:

https://github.com/ef4/liquid-fire

It has a standard CHANGELOG.md in the root folder.

Both "Update preview" and "Save and Track" buttons are inactive. In the bottom of the page, there's an error message:

'NoneType' object has no attribute 'lstrip'

Screenshot:

[svetlyak40wt]

Thank you, Andrey!