Comment 1 for bug 1747973

debug build:
==30885==ERROR: AddressSanitizer: heap-use-after-free on address 0x6080003275f8 at pc 0x7fffdc56d903 bp 0x7fffcdbd4be0 sp 0x7fffcdbd4bd8
READ of size 4 at 0x6080003275f8 thread T0

    #0 0x7fffdc56d902 in SHAPE_SEGMENT::GetWidth() const /home/twl/Kicad-dev/kicad-git-master/include/geometry/shape_segment.h:82:16
    #1 0x7fffdc56d7c8 in PNS::SEGMENT::Width() const /home/twl/Kicad-dev/kicad-git-master/pcbnew/router/./pns_segment.h:90:22
    #2 0x7fffdc626b5d in PNS::NODE::AssembleLine(PNS::SEGMENT*, int*, bool) /home/twl/Kicad-dev/kicad-git-master/pcbnew/router/pns_node.cpp:844:24
    #3 0x7fffdc6b0ca9 in PNS::LINE_PLACER::simplifyNewLine(PNS::NODE*, PNS::SEGMENT*) /home/twl/Kicad-dev/kicad-git-master/pcbnew/router/pns_line_placer.cpp:1105:21
    #4 0x7fffdc6b06a1 in PNS::LINE_PLACER::FixRoute(VECTOR2<int> const&, PNS::ITEM*) /home/twl/Kicad-dev/kicad-git-master/pcbnew/router/pns_line_placer.cpp:1025:9
    #5 0x7fffdc66d02d in PNS::ROUTER::FixRoute(VECTOR2<int> const&, PNS::ITEM*) /home/twl/Kicad-dev/kicad-git-master/pcbnew/router/pns_router.cpp:350:24
    #6 0x7fffdc598efa in ROUTER_TOOL::performRouting() /home/twl/Kicad-dev/kicad-git-master/pcbnew/router/router_tool.cpp:733:27
    #7 0x7fffdc59e839 in ROUTER_TOOL::mainLoop(PNS::ROUTER_MODE) /home/twl/Kicad-dev/kicad-git-master/pcbnew/router/router_tool.cpp:910:17
    #8 0x7fffdc59bf94 in ROUTER_TOOL::RouteSingleTrace(TOOL_EVENT const&) /home/twl/Kicad-dev/kicad-git-master/pcbnew/router/router_tool.cpp:832:12
    #9 0x7fffdc5a766a in int std::_Mem_fn_base<int (ROUTER_TOOL::*)(TOOL_EVENT const&), true>::operator()<TOOL_EVENT const&, void>(ROUTER_TOOL*, TOOL_EVENT const&) const /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/functional:600:11
    #10 0x7fffdc5a74fd in int std::_Bind<std::_Mem_fn<int (ROUTER_TOOL::*)(TOOL_EVENT const&)> (ROUTER_TOOL*, std::_Placeholder<1>)>::__call<int, TOOL_EVENT const&, 0ul, 1ul>(std::tuple<TOOL_EVENT const&>&&, std::_Index_tuple<0ul, 1ul>) /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/functional:1073:11
    #11 0x7fffdc5a72d8 in int std::_Bind<std::_Mem_fn<int (ROUTER_TOOL::*)(TOOL_EVENT const&)> (ROUTER_TOOL*, std::_Placeholder<1>)>::operator()<TOOL_EVENT const&, int>(TOOL_EVENT const&) /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/functional:1131:17
    #12 0x7fffdc5a6e01 in std::_Function_handler<int (TOOL_EVENT const&), std::_Bind<std::_Mem_fn<int (ROUTER_TOOL::*)(TOOL_EVENT const&)> (ROUTER_TOOL*, std::_Placeholder<1>)> >::_M_invoke(std::_Any_data const&, TOOL_EVENT const&) /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/functional:1856:9
    #13 0x7fffdca70718 in std::function<int (TOOL_EVENT const&)>::operator()(TOOL_EVENT const&) const /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/functional:2267:14
    #14 0x7fffdca7027a in COROUTINE<int, TOOL_EVENT const&>::callerStub(long) /home/twl/Kicad-dev/kicad-git-master/include/tool/coroutine.h:329:25
    #15 0x7fffdcb5aed0 in make_fcontext (/home/twl/Kicad-dev/kicad-build/debug-master/kicad/_pcbnew.kiface+0x1cbeed0)