World unload memory leak

[LaserSlime]

This plugin keeps references to worlds even after they are unloaded. This prevents the garbage collection from removing them properly, causing memory leaks in the long run.

From what I can tell you've already tried to prevent this by using WeakHashMap, but it's not working for some reason.

[Feniksovich]

In the latest implementation of the ServerWorldPropertiesRegistry world references are no longer stored in the WeakHashMap, but now holds a strong reference to a world which still prevents the world object from being removed by the GC. https://github.com/Moulberry/AxiomPaperPlugin/blob/cd8b5c534607cc59fd93425795741d106fde398f/src/main/java/com/moulberry/axiom/world_properties/server/ServerWorldPropertiesRegistry.java#L22 I guess it should be replaced with WeakReference<World> (or Reference<World> like in Bukkit location class).

private final WeakReference<World> world;

The only place where the ServerWorldPropertiesRegistry object is stored is the WeakHashMap: https://github.com/Moulberry/AxiomPaperPlugin/blob/cd8b5c534607cc59fd93425795741d106fde398f/src/main/java/com/moulberry/axiom/AxiomPaper.java#L327 But the value instance still holds strong reference to the world object equals the key, so neither World nor ServerWorldPropertiesRegistry instances won't be garbage collected.

[Moulberry]

Fixed by 26eb24f2084528a1b9dbd8daeea193cf2d2ec161