Provide default alt text to responsive tag to be used if asset has no alt text.

[cstilstra]

Is it possible for me to pass data to the responsive tag to be used in place of the asset's alt text ONLY in the case where the asset doesn't have alt text. As far as I can tell, the default behavior is that if I pass in data to the 'alt' parameter, that data will be displayed regardless of whether the underlying asset has alt text or not. Alternately, if I don't pass in any data to the 'alt' parameter, then the underlying asset's alt text will be used, even if it's empty. Does anybody know of a sensible way to achieve this?

[cstilstra]

Well, I realized that I can just customize the generated html to do what I'd like here.