When player has leaved/joined the game, console get error but not every time

[22:39:16] [ForkJoinPool-6-worker-1/ERROR] [ne.mi.ev.EventSubclassTransformer/EVENTBUS]: Could not find parent com/google/gson/reflect/TypeToken for class me/edoren/skin_changer/server/SkinProviderController$1 in classloader jdk.internal.loader.ClassLoaders$AppClassLoader@5a07e868 on thread Thread[ForkJoinPool-6-worker-1,8,SERVER]
[22:39:16] [ForkJoinPool-6-worker-1/ERROR] [ne.mi.ev.EventSubclassTransformer/EVENTBUS]: An error occurred building event handler
java.lang.ClassNotFoundException: com.google.gson.reflect.TypeToken
        at jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) ~[?:?] {}
        at jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) ~[?:?] {}
        at java.lang.ClassLoader.loadClass(ClassLoader.java:525) ~[?:?] {}
        at net.minecraftforge.eventbus.EventSubclassTransformer.buildEvents(EventSubclassTransformer.java:97) ~[eventbus-6.0.5.jar%2352!/:?] {}
        at net.minecraftforge.eventbus.EventSubclassTransformer.transform(EventSubclassTransformer.java:48) ~[eventbus-6.0.5.jar%2352!/:?] {}
        at net.minecraftforge.eventbus.EventBusEngine.processClass(EventBusEngine.java:26) ~[eventbus-6.0.5.jar%2352!/:?] {}
        at net.minecraftforge.eventbus.service.ModLauncherService.processClassWithFlags(ModLauncherService.java:32) ~[eventbus-6.0.5.jar%2352!/:6.0.5+6.0.5+master.eb8e549b] {}
        at cpw.mods.modlauncher.LaunchPluginHandler.offerClassNodeToPlugins(LaunchPluginHandler.java:88) ~[modlauncher-10.0.9.jar%2355!/:?] {}
        at cpw.mods.modlauncher.ClassTransformer.transform(ClassTransformer.java:120) ~[modlauncher-10.0.9.jar%2355!/:?] {}
        at cpw.mods.modlauncher.TransformingClassLoader.maybeTransformClassBytes(TransformingClassLoader.java:50) ~[modlauncher-10.0.9.jar%2355!/:?] {}
        at cpw.mods.cl.ModuleClassLoader.readerToClass(ModuleClassLoader.java:113) ~[securejarhandler-2.1.10.jar:?] {}
        at cpw.mods.cl.ModuleClassLoader.lambda$findClass$15(ModuleClassLoader.java:219) ~[securejarhandler-2.1.10.jar:?] {}
        at cpw.mods.cl.ModuleClassLoader.loadFromModule(ModuleClassLoader.java:229) ~[securejarhandler-2.1.10.jar:?] {}
        at cpw.mods.cl.ModuleClassLoader.findClass(ModuleClassLoader.java:219) ~[securejarhandler-2.1.10.jar:?] {}
        at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:135) ~[securejarhandler-2.1.10.jar:?] {}
        at java.lang.ClassLoader.loadClass(ClassLoader.java:525) ~[?:?] {}
        at me.edoren.skin_changer.server.SkinProviderController.readCacheFile(SkinProviderController.java:278) ~[?:?] {re:classloading}
        at me.edoren.skin_changer.server.SkinProviderController.loadPlayerDataFromCache(SkinProviderController.java:227) ~[?:?] {re:classloading}
        at me.edoren.skin_changer.server.SkinProviderController.lambda$onPlayerLogin$5(SkinProviderController.java:298) ~[?:?] {re:classloading}
        at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1395) ~[?:?] {}
        at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655) ~[?:?] {re:mixin,re:computing_frames}
        at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622) ~[?:?] {re:mixin,re:computing_frames}
        at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165) ~[?:?] {re:mixin}
edoren / SkinChanger

When player has leaved/joined the game, console get error but not every time #40
