Shulker Box can't be read by comparators if placed by dispensers until block update

When automatically placed by a dispenser, Shulker Boxes with items in their inventory do not output redstone signal through a comparator until a block update happens, either for the chest or the comparator.

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Can be fixed by calling the method net.minecraft.world.World.updateComparatorOutputLevel(BlockPos, Block) when the shulker box is dispensed.