don't access empty range list, could be rhbz#1180312
don't access empty range list, could be rhbz#1180312

ScRangeList::DeleteArea() may remove an entire range, if it was the
last range a subsequent call to ScConditionalFormat::DeleteArea() would
attempt to access an invalid first element.

Change-Id: I8d68c27963dc8561d61a94980093c271bd3aaffb

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core