Template not found; The template errors/404.null does not exist

[AMcBain]

This seems to happen on occasion for me, and I don't know what causes it. Basically Play! can't find something / a file, and tries to look up a template at "errors/404.null" instead of "errors/404.html". The problem being that when it can't find 404.null, it then results in a 500 error. The error stack-trace is below:

Internal Server Error (500) for request GET /gallery/images/lightbox-blank.gif

Template not found
The template errors/404.null does not exist.

play.exceptions.TemplateNotFoundException: Template not found : errors/404.null
        at play.templates.TemplateLoader.load(TemplateLoader.java:108)
        at play.mvc.results.NotFound.apply(NotFound.java:48)
        at play.mvc.ActionInvoker.invoke(ActionInvoker.java:248)
        at Invocation.HTTP Request(Play!)