Click on Step 4

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: pl.nataliana.bakingapp, PID: 4466
                  java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.exoplayer2.SimpleExoPlayer.setPlayWhenReady(boolean)' on a null object reference
                      at pl.nataliana.bakingapp.fragment.RecipeStepFragment.onPause(RecipeStepFragment.java:134)
                      at android.support.v4.app.Fragment.performPause(Fragment.java:2531)
                      at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1485)
                      at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1759)
                      at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:792)
                      at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2596)
                      at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2383)
                      at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2338)
                      at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:2215)
                      at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:649)
                      at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:167)
                      at android.support.v4.view.ViewPager.populate(ViewPager.java:1238)
                      at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:663)
                      at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:625)
                      at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:606)
                      at pl.nataliana.bakingapp.RecipeStepActivity$2.onTabSelected(RecipeStepActivity.java:89)
                      at android.support.design.widget.TabLayout.dispatchTabSelected(TabLayout.java:1165)
                      at android.support.design.widget.TabLayout.selectTab(TabLayout.java:1158)
                      at android.support.design.widget.TabLayout.selectTab(TabLayout.java:1128)
                      at android.support.design.widget.TabLayout$Tab.select(TabLayout.java:1427)
                      at android.support.design.widget.TabLayout$TabView.performClick(TabLayout.java:1537)
                      at android.view.View$PerformClick.run(View.java:22429)
                      at android.os.Handler.handleCallback(Handler.java:751)
                      at android.os.Handler.dispatchMessage(Handler.java:95)
                      at android.os.Looper.loop(Looper.java:154)
                      at android.app.ActivityThread.main(ActivityThread.java:6119)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)