We know that Mixxx tries to warn us that we are exiting mixxx when a deck is playing a track. It flashes the dialog that asks us "A deck is currently playing. Exit Mixxx?". However this does not happen when a sampler is playing a track. In such a case if an exit is issued, Mixxx simply exits without any warning. Though this may seem too trivial, but if we have a safeguard mechanism for currently playing decks, then why not for currently playing samples.
I also suggest that the warning be different for both cases. I am attaching a patch that fixes this bug. It works for a case in which both deck and sampler are playing. It first asks about the playing deck, if a "yes" is issued, it still asks about the playing sampler. According to what I observe, it must exit in the first, but anyhow it fixes all the possibilities.
I wonder if we could add this fix already in 1.10.1 and not just in 1.11.0 because it contains no new functionality and eliminates an issue with the current version instead.