Blender Git Loki

Fix T53476: File Browser: Selection Issue with 'fill' option.

Fill-selection would only go upward in list of items to find an already
selected one and fill-select all items in-between. Now, in case upward
search fails, it will also intent to go downward, effectiviely allowing
to 'fill-select' from bottom to top.

Note that top-to-bottom keeps priority (i.e. if a top-to-bottom
fill-selection is possible, it will always happen, even if a
bottom-to-top one is also possible).