Don't throw an exception when Skript has weird load behaviour (#8422)

Author: TheLimeGlass

src/main/java/ch/njol/skript/structures/StructAutoReload.java

@@ -146,7 +146,8 @@ public void run() {
 
 	@Override
 	public void unload() {
-		task.cancel();
+		if (task != null)
+			task.cancel();
 	}
 
 	@Override