[BUG] Application crashes when left on background

[Aletibazo]

Describe the bug
App crashes when reopening it after going into the background for a short period of time with the following error:

2019-05-10 19:44:20.715 28514-28514/com.gymkhanachain.app E/AndroidRuntime: FATAL EXCEPTION: main Process: com.gymkhanachain.app, PID: 28514 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gymkhanachain.app/com.gymkhanachain.app.ui.mainscreen.activity.MainActivity}: java.lang.IllegalArgumentException: No view found for id 0x7f0900a1 (com.gymkhanachain.app:id/map_placeholder) for fragment MapFragment{d984f5b #9 id=0x7f0900a1} at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2814) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892) at android.app.ActivityThread.-wrap11(Unknown Source:0) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1613) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:176) at android.app.ActivityThread.main(ActivityThread.java:6635) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823) Caused by: java.lang.IllegalArgumentException: No view found for id 0x7f0900a1 (com.gymkhanachain.app:id/map_placeholder) for fragment MapFragment{d984f5b #9 id=0x7f0900a1} at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1454) at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1784) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1852) at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:802) at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625) at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411) at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273) at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3273) at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:3229) at android.support.v4.app.FragmentController.dispatchActivityCreated(FragmentController.java:201) at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:620) at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:178) at com.gymkhanachain.app.ui.mainscreen.activity.MainActivity.onStart(MainActivity.java:119) at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1335) at android.app.Activity.performStart(Activity.java:7104) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2777)

To Reproduce
Steps to reproduce the behavior:

1. Open App
2. Press Home button
3. Use the phone for a few minutes
4. App crashes

Expected behavior
After reopening the app it should load it's previous state.

Smartphone (please complete the following information):

• OS version: Android 8.1.0
• APK version: Commit 3db7424