bug: undo in formula

[Eran Tromer]

Open a new document and type:

M-m [        // You get "[]|" where | denotes cusror
             // (note wrong cursor position -- bug by itself!)
<left> x     // You get "[x|]"
S-<left> y   // You get "[y|]"
C-z          // Formula is now empty, which is incorrect.


Tested on yesterday's 1.2.0cvs (sheesh does LyX take a long time to
build!).

  Regards,
    Eran Tromer