787 -- Eliminate segfaults due to empty list and unitialized properties (issue163048)

[n . puttock]

LGTM.


http://codereview.appspot.com/163048/diff/1/2
File lily/script-column.cc (left):

http://codereview.appspot.com/163048/diff/1/2#oldcode161
lily/script-column.cc:161: g->set_property ("outside-staff-priority",
indent
(+ following lines)

http://codereview.appspot.com/163048/diff/1/2#oldcode168
lily/script-column.cc:168: g->set_property (
indent
(+ following lines)

http://codereview.appspot.com/163048/diff/1/2
File lily/script-column.cc (right):

http://codereview.appspot.com/163048/diff/1/2#newcode148
lily/script-column.cc:148: first =  unsmob_grob (scm_car (ss));
indent
extra space after =

http://codereview.appspot.com/163048/diff/1/2#newcode149
lily/script-column.cc:149: default_outside_staff =
first->get_property("outside-staff-priority");
indent

get_property (

http://codereview.appspot.com/163048/diff/1/2#newcode169
lily/script-column.cc:169: robust_scm2double (last_outside_staff, 0) +
0.1));
scm_to_double (last_outside_staff) (it must be a number since it's
inside the `if' block)

http://codereview.appspot.com/163048/diff/1/2#newcode177
lily/script-column.cc:177: scm_from_double (robust_scm2double
(last_outside_staff, 0) +
scm_to_double (last_outside_staff)

http://codereview.appspot.com/163048