E FATAL EXCEPTION: main
Process: com.example.gyaanquiz, PID: 6781
java.lang.RuntimeException: Unable to resume activity {com.example.gyaanquiz/com.example.gyaanquiz.QuizActivity}: java.lang.NullPointerException: Attempt to invoke virtual method ‘android.os.CountDownTimer android.os.CountDownTimer.start()’ on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3858)

at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3890)
at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:51)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:150)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:73)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1858)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:201)
at android.app.ActivityThread.main(ActivityThread.java:6820)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:922)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method ‘android.os.CountDownTimer android.os.CountDownTimer.start()’ on a null object reference
at com.example.gyaanquiz.QuizActivity.onResume(QuizActivity.java:378)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1413)
at android.app.Activity.performResume(Activity.java:7400)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3850)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3890) 
at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:51) 
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:150) 
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:73) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1858) 
at android.os.Handler.dispatchMessage(Handler.java:106) 
at android.os.Looper.loop(Looper.java:201) 
at android.app.ActivityThread.main(ActivityThread.java:6820) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:922) 

I don’t what to do now. I have tried every way I could find.