fix: properly unregister chunk loader

When a minecart is registered by a dispenser, then deregistered and re‑registered without ever moving, the chunk never loads because the lastChunkPos is never reset

Author: Smalldero

src/main/java/io/nihlen/scriptschunkloaders/mixin/AbstractMinecartEntityMixin.java

@@ -84,6 +84,7 @@ private void injectConstructor(CallbackInfo callbackInfo) {
 
 	public void scripts_chunk_loaders$stopChunkLoader() {
 		scripts_chunk_loaders$stopChunkLoader(false);
+		this.lastChunkPos = null;
 	}
 	public void scripts_chunk_loaders$stopChunkLoader(Boolean keepName) {
 		this.isChunkLoader = false;