java.lang.IllegalStateException: Could not execute method for android:onClick
	at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:414)
	at android.view.View.performClick(View.java:7394)
	at android.view.View.performClickInternal(View.java:7348)
	at android.view.View.access$3900(View.java:827)
	at android.view.View$PerformClick.run(View.java:28293)
	at android.os.Handler.handleCallback(Handler.java:899)
	at android.os.Handler.dispatchMessage(Handler.java:100)
	at android.os.Looper.loop(Looper.java:238)
	at android.app.ActivityThread.main(ActivityThread.java:7853)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:984)
Caused by: java.lang.reflect.InvocationTargetException
	at java.lang.reflect.Method.invoke(Native Method)
	at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409)
	... 11 more
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.vision.Detector.release()' on a null object reference
	at com.google.android.gms.vision.CameraSource$zzb.release(Unknown Source:8)
	at com.google.android.gms.vision.CameraSource.release(Unknown Source:3)
	at com.entitcs.office_attendance.camera.FaceTrackerActivity.groupAttendance(FaceTrackerActivity.java:449)
	... 13 more