From a bug report, applying unlit Candelabrum
of Invocation when its candles had 1 turn's worth of burning left would
give a message that the candles were burning but not actually light them
if done anywhere other than the invocation location. Their burn time is
cut it half when not at that spot, and dividing an age of 1 yielded 0,
confusing begin_burn(). They wouldn't light and they couldn't be replaced
since they'd never get used up.
The problem is real, but the chance of it actually happening in
normal play is just about zero. This applies his suggested fix of
rounding the halved burn time up instead of down so that it can't yield 0.
It also applies his suggestion that the Candelabrum treat the invocation
spot like any other location once invocation has produced stairs there,
just as the Bell and the Book do.
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