This commit fixes a crash when accessing a math inset. This was due to an invalid...

This commit fixes a crash when accessing a math inset. This was due to an invalid CursorSlice::text() null pointer accessed in InsetMathNest::cursorPos():

    CoordCache & coord_cache = sl.text()->bv()->coordCache();

As you can see, I used this indirection to access the BufferView::CoordCache(). Bad luck, the passed CursorSlice was not completely valid inside a mathed inset, hence the crash. My solution is to pass BufferView to InsetBase::cursorPos() and all its derivative.

* InsetBase::cursorPos(): pass BufferView const &

* bufferview_funcs::coordOffset(): ditto.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@15356 a592a061-630c-0410-9148-cb99ea01b6c8