New "dryingrack" component not consistently checking for item w/ acid check

The new "dryingrack" component, when it is acid raining, does not check for the item before attempting to get perishable information.

This is inconsistent with the non-acid rain logic.

Since it is normally possible to call Preserver:GetPerishRateMultiplier without an inst (typically from mods), it would be great if this was fixed, especially as it seems the typical behaviour for the custom preserver functions is to either return a rate or nil.