Exporting an audio note causes NullPointerException

[Kobayashi-996]

Environment

Android: Android 9.0
App Version: 1.4.1

Steps

1. Open the app
2. Create new audio
3. Click "More options"
4. Click "Export" and the app crashes

ScreenRecord

test.mp4

Logcat

FATAL EXCEPTION: main
Process: org.secuso.privacyfriendlynotes, PID: 23372
java.lang.NullPointerException
at org.secuso.privacyfriendlynotes.ui.notes.AudioNoteActivity.onSaveExternalStorage(AudioNoteActivity.kt:286)
at org.secuso.privacyfriendlynotes.ui.notes.BaseNoteActivity.saveToExternalStorage(BaseNoteActivity.kt:477)
at org.secuso.privacyfriendlynotes.ui.notes.BaseNoteActivity.onOptionsItemSelected(BaseNoteActivity.kt:269)
at android.app.Activity.onMenuItemSelected(Activity.java:3543)
at androidx.activity.ComponentActivity.onMenuItemSelected(ComponentActivity.java:514)
at androidx.fragment.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:352)
at androidx.appcompat.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:266)
at androidx.appcompat.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:110)
at androidx.appcompat.app.AppCompatDelegateImpl.onMenuItemSelected(AppCompatDelegateImpl.java:1189)
at androidx.appcompat.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:836)
at androidx.appcompat.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:159)
at androidx.appcompat.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:987)
at androidx.appcompat.view.menu.MenuPopup.onItemClick(MenuPopup.java:128)
at android.widget.AdapterView.performItemClick(AdapterView.java:318)
at android.widget.AbsListView.performItemClick(AbsListView.java:1159)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3136)
at android.widget.AbsListView$3.run(AbsListView.java:4052)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)