Checks to see if tuplet brackets have bounds (issue 13582046)

[dak]

https://codereview.appspot.com/13582046/diff/1/lily/tuplet-bracket.cc
File lily/tuplet-bracket.cc (right):

https://codereview.appspot.com/13582046/diff/1/lily/tuplet-bracket.cc#newcode99
lily/tuplet-bracket.cc:99: if (!left || !right)
Too many combinatorics involved unnecessarily.  Just do
if (!left || left->break_status_dir ())
first, and then the same for right.  Then one does not need to track the
combination of left/right states at the same time in order to figure out
which cases are caught.

At any rate, this does not appear to give us a beam: it just avoids a
crash.  And there is no explanation of why this code would be called now
when it wasn't called before issue 3199.

Not sure whether one would call this related to issue 3299: issue 3299
is for the case where _no_ other rhythmic elements share the time of the
spacer rest.  Which is the case in the minimal example of the bug report
but possibly not the only situation triggering the bug.

At any rate, this appears to be a symptomatic patch replacing a crash
with a programming error and/or a bad result.  Which is an improvement
but still seems to fall short of useful behavior.

https://codereview.appspot.com/13582046/