android-NullPointerException: Attempt to invoke virtual method p()

I'm using Crashlytics to monitor crashes of my Android app. the following crash has been reported for some users:

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'void app.mapdroid.activities.MapActivity.p()' on a null object reference
   at app.mapdroid.fragments.InfinityFragment$2.run(InfinityFragment.java:8)
   at android.os.Handler.handleCallback(Handler.java:790)
   at android.os.Handler.dispatchMessage(Handler.java:99)
   at android.os.Looper.loop(Looper.java:164)
   at android.app.ActivityThread.main(ActivityThread.java:6543)
   at java.lang.reflect.Method.invoke(Method.java)
   at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:440)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:810)

I don't understand what is p() method which is causing this crash. can anyone guide please?

the app has been reported to be in background state for all users with proximity on.