Remove content when dismissing

[Continuation of https://github.com/gothfox/Tiny-Tiny-RSS/pull/230#issuecomment-19809758]
This patch removes the content when an article is dismissed. It seemed to work in the (admittedly few) tests I did, but I'm not familiar enough with the codebase to know if the element removed is needed/used anywhere else. A quick `git grep CICD` doesn't turn up anything besides the functions for expanding/collapsing the content, which shouldn't happen if the article is dismissed.
It also seems to work in non-combined mode.
There's a random fix in the exception handling code. I can put this in a different pull request if you want.