java.lang.IllegalStateException: Could not execute method for android:onClick
	at androidx.appcompat.app.AppCompatViewInflater$a.onClick(Unknown Source:34)
	at android.view.View.performClick(View.java:7503)
	at android.view.View.performClickInternal(View.java:7480)
	at android.view.View.access$3600(View.java:813)
	at android.view.View$PerformClick.run(View.java:28445)
	at android.os.Handler.handleCallback(Handler.java:938)
	at android.os.Handler.dispatchMessage(Handler.java:99)
	at android.os.Looper.loop(Looper.java:223)
	at android.app.ActivityThread.main(ActivityThread.java:7948)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:603)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: java.lang.reflect.InvocationTargetException
	at java.lang.reflect.Method.invoke(Native Method)
	at androidx.appcompat.app.AppCompatViewInflater$a.onClick(Unknown Source:25)
	... 11 more
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.vision.b.d()' on a null object reference
	at com.google.android.gms.vision.a$e.a(Unknown Source:2)
	at com.google.android.gms.vision.a.c(Unknown Source:8)
	at com.entitcs.office_attendance.camera.FaceTrackerActivity.groupAttendance(Unknown Source:2)
	... 13 more