GtkFileChooser: reveal selection after sorting view

Open Nelson Ben requested to merge BUG_reveal_after_sort_GTK3 into gtk-3-24
After clicking on any of the sort column headers,
the view is properly resorted but the file we had
selected can probably be now out of view due to
the new sort order.

This commit just makes sure to reveal the current
file selection (if any) after the view has been

Closes #2683

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