bug fix: make fluxbox work under nxserver, closes #2813828
bug fix: make fluxbox work under nxserver, closes #2813828

nxserver-3.x creates a XExposeEvent for the unmapped FbTk::Menu(), which is
not configured completely yet (hence unmapped). this causes a call to
FbTk::Menu::clearItem() which then uses a value of 0 for m_rows_per_column
to divide the current index which triggers a SIGFPE.

it is still unclear, why nxserver-3.x creates the XExposeEvent for the
unmapped (menu) window. doing nothing if the menu is unmapped 'fixes'
the problem for now.

many thanks to Lars Engels (bsd-geek.de) to assist me in debugging this
issue.

luebking/fluxbox,luebking/fluxbox,naimdjon/fluxbox,naimdjon/fluxbox,Arkq/fluxbox,luebking/fluxbox,lukoko/fluxbox,Arkq/fluxbox,luebking/fluxbox,lukoko/fluxbox,olivergondza/fluxbox,lukoko/fluxbox,Arkq/fluxbox,lukoko/fluxbox,lukoko/fluxbox,luebking/fluxbox,olivergondza/fluxbox,Arkq/fluxbox,naimdjon/fluxbox,olivergondza/fluxbox,Arkq/fluxbox,olivergondza/fluxbox,naimdjon/fluxbox,olivergondza/fluxbox,naimdjon/fluxbox