Fix crashing after cancel not existing notification

[sashkooo]

After cancel not existing notification, if I set new, it crashes with log:

AndroidRuntime: Caused by: java.lang.RuntimeException: Unable to start receiver net.agasper.unitynotification.UnityNotificationManager: java.lang.NullPointerException AndroidRuntime: at android.app.ActivityThread.handleReceiver(ActivityThread.java:2739) AndroidRuntime: at android.app.ActivityThread.access$1800(ActivityThread.java:153) AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1428) AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:102) AndroidRuntime: at android.os.Looper.loop(Looper.java:148) AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5441) AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method) AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:738) AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:628) AndroidRuntime: Caused by: java.lang.NullPointerException AndroidRuntime: at java.lang.Class.classForName(Native Method) AndroidRuntime: at java.lang.Class.forName(Class.java:324) AndroidRuntime: at java.lang.Class.forName(Class.java:285) AndroidRuntime: at net.agasper.unitynotification.UnityNotificationManager.onReceive(UnityNotificationManager.java:95) AndroidRuntime: at android.app.ActivityThread.handleReceiver(ActivityThread.java:2732) AndroidRuntime: ... 8 more ActivityManager: Invalid thumbnail dimensions: 0x0

[sashkooo]

Please, rebuild jar because I committed only src

[Agasper]

@sashkooo i will be very appreciated if you can do it, because i don't have now any devices where i can do it