I have this plugin installed along with my trac and found this bug recently which can be quite annoying and confusing to the users.
This happens only when the user is creating a new ticket and attaching a screenshot using the plugin. The ticket gets created, the user is able to paste the screenshot, but when he hits "Send the screenshot" he is redirected to an empty page like the one attached.
The problem is a missing trailing slash "/" in the URL. The page is redirected to "/attachment/ticket/183" for example while it should have been redirected to "/attachment/ticket/183/".
It would be great if someone would look into this.