Crash on collapse/expand collapsable inset

[Rob Bearman]

Launch LyX, create new file, insert box inset (or perhaps any
collapsable inset), click on button to collapse, click on it again. This
crashes LyX. A portion of the Windows stack trace included. I see this
on both Windows and Mac.

        lyx.exe!lyx::support::abort()  Line 23  C++
        lyx.exe!boost::assertion_failed(const char * expr=0x0093cc7c,
const char * function=0x0093cc44, const char * file=0x0093cc24, long
line=30)  Line 57       C++
        lyx.exe!lyxbreaker(const void * data=0x010b3008, const char *
hint=0x009ac3e4, int size=0)  Line 30 + 0x1c    C++
        lyx.exe!CoordCacheBase<InsetBase>::check(const InsetBase *
thing=0x010b3008, const char * hint=0x009ac3e4)  Line 92 + 0x16 C++
        lyx.exe!CoordCacheBase<InsetBase>::x(const InsetBase *
thing=0x010b3008)  Line 60      C++
        lyx.exe!InsetBase::xo()  Line 328       C++
        lyx.exe!InsetCollapsable::getCursorPos(const CursorSlice &
sl={...}, int & x=0, int & y=0)  Line 199 + 0x8 C++
        lyx.exe!bv_funcs::coordOffset(const DocIterator & dit={...})
Line 166        C++
        lyx.exe!bv_funcs::getPos(const DocIterator & dit={...})  Line
195 + 0xd       C++
        lyx.exe!LCursor::getPos(int & x=0, int & y=0)  Line 312 + 0xd
C++
        lyx.exe!LyXScreen::showCursor(BufferView & bv={...})  Line 195
C++
        lyx.exe!LyXScreen::toggleCursor(BufferView & bv={...})  Line 226
C++
        lyx.exe!BufferView::Pimpl::cursorToggle()  Line 666     C++

Thanks
Rob