oh, and here's a backtrace:

(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007f8ad49fb4ea in __GI_abort () at abort.c:118
#2  0x00007f8ad49f2e37 in __assert_fail_base (fmt=<optimized out>, assertion=assertion@entry=0x7f8ade89a1cc "this->is_initialized()", 
    file=file@entry=0x7f8ade89a248 "/usr/include/boost/optional/optional.hpp", line=line@entry=868, 
    function=function@entry=0x7f8ade9b0280 "boost::optional<T>::reference_type boost::optional<T>::get() [with T = Geom::Rect; boost::optional<T>::reference_type = Geom::Rect&]") at assert.c:92
#3  0x00007f8ad49f2ee2 in __GI___assert_fail (assertion=0x7f8ade89a1cc "this->is_initialized()", file=0x7f8ade89a248 "/usr/include/boost/optional/optional.hpp", 
    line=868, 
    function=0x7f8ade9b0280 "boost::optional<T>::reference_type boost::optional<T>::get() [with T = Geom::Rect; boost::optional<T>::reference_type = Geom::Rect&]")
    at assert.c:101
#4  0x00007f8ade84cbf4 in Geom::Sweeper<Geom::PathIntersectionSweepSet>::process() () from /usr/bin/../lib/inkscape/libinkscape_base.so
#5  0x00007f8ade84b65e in Geom::PathVector::intersect(Geom::PathVector const&, double) const () from /usr/bin/../lib/inkscape/libinkscape_base.so
#6  0x00007f8ade617f31 in Inkscape::ObjectSnapper::_snapPathsConstrained(IntermSnapResults&, Inkscape::SnapCandidatePoint const&, Inkscape::Snapper::SnapConstraint const&, Geom::Point const&) const () from /usr/bin/../lib/inkscape/libinkscape_base.so
#7  0x00007f8ade61901c in Inkscape::ObjectSnapper::constrainedSnap(IntermSnapResults&, Inkscape::SnapCandidatePoint const&, Geom::OptRect const&, Inkscape::Snapper::SnapConstraint const&, std::vector<SPItem const*, std::allocator<SPItem const*> > const*, std::vector<Inkscape::SnapCandidatePoint, std::allocator<Inkscape::SnapCandidatePoint> >*) const () from /usr/bin/../lib/inkscape/libinkscape_base.so
#8  0x00007f8ade65c71e in SnapManager::constrainedSnap(Inkscape::SnapCandidatePoint const&, Inkscape::Snapper::SnapConstraint const&, Geom::OptRect const&) const ()
   from /usr/bin/../lib/inkscape/libinkscape_base.so
#9  0x00007f8ade625e8f in Inkscape::PureScale::snap(SnapManager*, Inkscape::SnapCandidatePoint const&, Geom::Point, Geom::OptRect const&) const ()
   from /usr/bin/../lib/inkscape/libinkscape_base.so
#10 0x00007f8ade626a23 in Inkscape::PureTransform::snap(SnapManager*, std::vector<Inkscape::SnapCandidatePoint, std::allocator<Inkscape::SnapCandidatePoint> > const&, Geom::Point const&) () from /usr/bin/../lib/inkscape/libinkscape_base.so
#11 0x00007f8ade65867b in SnapManager::snapTransformed(std::vector<Inkscape::SnapCandidatePoint, std::allocator<Inkscape::SnapCandidatePoint> > const&, Geom::Point const&, Inkscape::PureTransform&) () from /usr/bin/../lib/inkscape/libinkscape_base.so
#12 0x00007f8ade64dffd in Inkscape::SelTrans::scaleRequest(Geom::Point&, unsigned int) () from /usr/bin/../lib/inkscape/libinkscape_base.so
#13 0x00007f8ade650ce0 in Inkscape::SelTrans::handleRequest(SPKnot*, Geom::Point*, unsigned int, SPSelTransHandle const&) ()
   from /usr/bin/../lib/inkscape/libinkscape_base.so
#14 0x00007f8ade653d4f in sigc::internal::slot_call<sigc::bind_functor<-1, sigc::pointer_functor4<SPKnot*, Geom::Point*, unsigned int, SPSelTransHandle const*, int>, SPSelTransHandle const*, sigc::nil, sigc::nil, sigc::nil, sigc::nil, sigc::nil, sigc::nil>, bool, SPKnot*, Geom::Point*, unsigned int>::call_it(sigc::internal::slot_rep*, SPKnot* const&, Geom::Point* const&, unsigned int const&) () from /usr/bin/../lib/inkscape/libinkscape_base.so
#15 0x00007f8ade608bb6 in SPKnot::requestPosition(Geom::Point const&, unsigned int) () from /usr/bin/../lib/inkscape/libinkscape_base.so
#16 0x00007f8ade608d0f in sp_knot_handler_request_position(_GdkEvent*, SPKnot*) () from /usr/bin/../lib/inkscape/libinkscape_base.so
#17 0x00007f8ade2b87b1 in Inkscape::UI::Tools::sp_event_context_snap_watchdog_callback(void*) () from /usr/bin/../lib/inkscape/libinkscape_base.so
#18 0x00007f8adbb7c123 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#19 0x00007f8adbb7b6aa in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#20 0x00007f8adbb7ba60 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#21 0x00007f8adbb7bd82 in g_main_loop_run () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#22 0x00007f8ad82d43b7 in gtk_main () from /lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#23 0x000055bad5d3885b in sp_main_gui(int, char const**) ()
#24 0x00007f8ad49e72b1 in __libc_start_main (main=0x55bad5d36350 <main>, argc=2, argv=0x7ffc3d7ad558, init=<optimized out>, fini=<optimized out>, 
    rtld_fini=<optimized out>, stack_end=0x7ffc3d7ad548) at ../csu/libc-start.c:291
#25 0x000055bad5d368ba in _start ()