[Bug] Crash when using custom tab back button

[bsurd]

Steps to reproduce

1. Open a custom tab.
2. Press the back button.

Expected behavior

You are taken to the previous app from where the custom tab was opened.

Actual behavior

The app crashes.

Device information

• Android device:
  • OnePlus 5T (Android 9)
  • Nexus 6P (Android 8.1)
• Fenix version: 5/13
• Video
• Could be related to [Bug] RuntimeExceptionandroid.app.ActivityThread in callActivityOnStop - Crash when closing a custom tab #2414 ?

┆Issue is synchronized with this Jira Task

[cadeyrn]

Exception:

2019-05-13 20:55:45.320 6981-6981/org.mozilla.fenix.debug E/AndroidRuntime: FATAL EXCEPTION: main
    Process: org.mozilla.fenix.debug, PID: 6981
    java.lang.RuntimeException: Unable to stop activity {org.mozilla.fenix.debug/org.mozilla.fenix.customtabs.CustomTabActivity}: java.lang.IllegalArgumentException: Required value was null.
        at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:4670)
        at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:4737)
        at android.app.ActivityThread.-wrap5(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1710)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:180)
        at android.app.ActivityThread.main(ActivityThread.java:6950)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:835)
     Caused by: java.lang.IllegalArgumentException: Required value was null.
        at org.mozilla.fenix.browser.BrowserFragment.getSessionById(BrowserFragment.kt:689)
        at org.mozilla.fenix.browser.BrowserFragment.onStop(BrowserFragment.kt:509)
        at androidx.fragment.app.Fragment.performStop(Fragment.java:2836)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:933)
        at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1228)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1293)
        at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManagerImpl.java:2646)
        at androidx.fragment.app.FragmentManagerImpl.dispatchStop(FragmentManagerImpl.java:2621)
        at androidx.fragment.app.Fragment.performStop(Fragment.java:2832)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:933)
        at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1228)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1293)
        at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManagerImpl.java:2646)
        at androidx.fragment.app.FragmentManagerImpl.dispatchStop(FragmentManagerImpl.java:2621)
        at androidx.fragment.app.FragmentController.dispatchStop(FragmentController.java:290)
        at androidx.fragment.app.FragmentActivity.onStop(FragmentActivity.java:564)
        at androidx.appcompat.app.AppCompatActivity.onStop(AppCompatActivity.java:207)
        at android.app.Instrumentation.callActivityOnStop(Instrumentation.java:1454)
        at android.app.Activity.performStop(Activity.java:7161)

[lobontiumira]

Closing this as a dupe of #2414