min can't possibly be un-initialized, since poll(2) returns zero only when the timeout expires. However, this should please some checkers (looking at you, fortify/string.h!) and doesn't cost anything.

not that we're particularly smart now, but libgrapheme gives us a nice result in the scripts I tried.

in case i == base->ntimers bubbledown() won't do anything, but it's still better to pass an index that we know is valid.