[After a moment, Filbo manages to get some of the cheer up. Maybe it's him forcing it a little]

O-Oh, well, they probably won't...but it should be fine! I mean, I have been on fire before, it's not so bad as long as you know what to do!

[He decides not to mention that grumpus fur seems to be, uh...kind of astonishingly flammable, but hey, for some reason they can stay generally unharmed while being on fire for a while and he knows it due to, well, personal experience, so he tries not to worry too much]