crash when resizing in snapping mode

[anarcat]

When resizing the "apt-get install anarchism" logo on the "meta" (or "tux" or "windows") key at the bottom left of the keyboard in the attached diagram, Inkscape crashes violently with:

Warning: limit of 200 snap sources reached, some will be ignored
inkscape: /usr/include/boost/optional/optional.hpp :868 : boost::optional<T>::reference_type boost::optional<T>::get() [with T = Geom::Rect; boost::optional<T>::reference_type = Geom::Rect&]: l'assertion « this->is_initialized() » a échoué.

Emergency save activated!

Emergency save document locations:
  /home/anarcat/src/apt-install-anarchism/wasd-keyboard.svg.2017_11_15_14_06_00.0.svg
Emergency save completed. Inkscape will close now.
If you can reproduce this crash, please file a bug at www.inkscape.org
with a detailed description of the steps leading to the crash, so we can fix it.
Complété

If snapping is disabled, the element can be resized properly.

To reproduce:

 1. open the file
 2. zoom onto one of the "meta" keys
 3. click on the apt-get install anarchism logo
 4. grab one of the handles, press control and shift to keep the ratio right and move

Make sure snapping is enabled otherwise this won't crash.

[anarcat (anarcat)]

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, si...