Small fix thanks to D.R.   Boxhoorn (In the destructor it is possible the mallib object is allready destroyed, ie  we check for this case now)
Small fix thanks to D.R.   Boxhoorn
(In the destructor it is possible the mallib object is allready destroyed, ie
 we check for this case now)

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb