* fix bug 4055, overdue patch from Stefan Schimanski:

* fix bug 4055, overdue patch from Stefan Schimanski:

"The idea of the beforeDispX/Y_ variables in the Cursor is to hold the position
of the cursor on screen before the lyxfunc is dispatched. But to get this the
metrics must be valid. It's updated in Cursor::dispatch before the dispatch
loop.
After inserting/deleting stuff (like when deleting the selected text before
inserting the alpha) the metrics are invalid. But the handler for the alpha
calls Cursor::dispatch after the deletion and hence the crash with your second
patch.

Here is a patch fixing that:

The beforeDispatchXY variable do not belong into the Cursor::dispatch because
Cursor::dispatch is often called "manually" by many handlers to some followup
action. So this logic must go somewhere else where it is sure that is not
updated after the metrics got invalidated."

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@22193 a592a061-630c-0410-9148-cb99ea01b6c8