In addon:UpdateFilters(): Set the recipe's "is_visible" member to nil instead of false.

diff --git a/ARL.lua b/ARL.lua
index 937fdea..6822936 100644
--- a/ARL.lua
+++ b/ARL.lua
@@ -1549,7 +1549,7 @@ do
 			else
 				can_display = false
 			end
-			recipe.is_visible = can_display
+			recipe.is_visible = can_display or nil
 		end
 		Player.recipes_total = recipes_total
 		Player.recipes_known = recipes_known