sending :alt => nil to an image tag should omit the images alt tag

I have an app where I set the alt tag of images with javascript. To reduce the size of the page, I want to emit img tags with no alt attribute, however that is not currently possible:

image_tag "foo.png", :alt => nil # => <img alt="Foo" src="/images/foo.png" />

I agree that images should have alt tags, and I agree that the default is sensible. However, if I explicitly send :alt => nil, I expect it to omit the alt attribute altogether, to be consistent with :class and other html attributes.

I plan to submit a patch momentarily.