Should an empty thumbnail template tag raise an exception?

[khink]

According to https://sorl-thumbnail.readthedocs.io/en/latest/examples.html#template-examples, a thumbnail template tag requires at least an image argument and a geometry string: {% thumbnail item.image "100x100" %}

However, an empty tag {% thumbnail %} does not give an error (as omitting the geometry string does). I checked this with THUMBNAIL_DEBUG = True.

One time when the error surfaces is when running django-compressor's ./manage.py compress. This results in an IndexError list index out of range from sorl/thumbnail/templatetags/thumbnail.py in __init__ at line 96:

    def __init__(self, parser, token):
        bits = token.split_contents()
        self.file_ = parser.compile_filter(bits[1])

Turns out that i hadn't been paying attention while copy/pasting a lot of thumbnail tags, and instead of {% endthumbnail %} i'd put {% thumbnail %}.

I think it would be better if sorl.thumbnail raises an exception on empty template thumbnail tags, especially if THUMBNAIL_DEBUG = True, because empty tags do nothing and can only be an error.