Fix MediaView::getSelection

Fix MediaView::getSelection

The selection in MediaView::getSelection doesn't work ok as
the internal table is sized using the number of selected items
and not the number of rows in the total table. But the table
is indexed using a row number which can be any rownr of the
total of the table. Things seen is that 3 rows are selected
but the selection only returns 2. This is probably a side effect
because the code could also just have crashed as nb = 16 and
rownr = 29-31 e.g. addressed outside the bounds of the array.

Changed the internal array to use bools instead of ints so
its also somewhat smaller.