fix "Comparison method violates its general contract" error

[SleepyPrince]

I have been having occasional crashes when sort containers

java.lang.IllegalArgumentException: Comparison method violates its general contract!
    at java.base/java.util.TimSort.mergeLo(TimSort.java:781)
    at java.base/java.util.TimSort.mergeAt(TimSort.java:518)
    at java.base/java.util.TimSort.mergeCollapse(TimSort.java:448)
    at java.base/java.util.TimSort.sort(TimSort.java:245)
    at java.base/java.util.Arrays.sort(Arrays.java:1308)
    at java.base/java.util.ArrayList.sort(ArrayList.java:1804)
    at net.frostbyte.inventory.InventorySorter.getSortedStackArray(InventorySorter.java:129)
    at net.frostbyte.inventory.InventorySorter.sortStacks(InventorySorter.java:137)
    at net.frostbyte.inventory.InventorySorter.onEndTick(InventorySorter.java:51)
    at net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientTickEvents.lambda$static$2(ClientTickEvents.java:43)
    at net.minecraft.class_310.handler$zmc000$fabric-lifecycle-events-v1$onEndTick(class_310.java:6247)
    at net.minecraft.class_310.method_1574(class_310.java:2063)
    at net.minecraft.class_310.method_1523(class_310.java:1281)
    at net.minecraft.class_310.method_1514(class_310.java:888)
    at net.minecraft.client.main.Main.main(Main.java:265)
    at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:470)
    at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:74)
    at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)

I am not fully familiar with java but I believe that java is not happy that the return 0 case is not present in the code. I tried the code change on a chest that kept crashing when I sort it and it seems to be working.