And, at the end of the day this was a really trivial problem. It could be fixed at any time, in a few seconds, by simply hitting Ctrl+R. It's nice that this memory leak is fixed, but I hope the devs focus their time and energy on adding or improving functionality rather than hunting down these kinds of bugs.
Or, to put it this way: a great many people might be affected by some random issue that stops their workflow in some manner (like a new device which yet has no calibre plugin). There are very few people who have the competence and inclination to hack calibre effectively. What would you prefer them to do: help those people or add some nifty conversion feature, or hunt down very minor annoyances with trivial workarounds?
Of course each developer chooses what they'd like to improve, but I know what I'd like them to focus on.