java.lang.NullPointerException: throw with null exception
	at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:1)
	at org.liberty.android.fantastischmemo.ui.PreviewEditActivity.deleteCard(PreviewEditActivity.java:1)
	at org.liberty.android.fantastischmemo.ui.PreviewEditActivity.onOptionsItemSelected(PreviewEditActivity.java:64)
	at android.app.Activity.onMenuItemSelected(Activity.java:2908)
	at androidx.fragment.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:1)
	at androidx.appcompat.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:1)
	at androidx.appcompat.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:1)
	at androidx.appcompat.app.AppCompatDelegateImpl.onMenuItemSelected(AppCompatDelegateImpl.java:4)
	at androidx.appcompat.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:1)
	at androidx.appcompat.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:2)
	at androidx.appcompat.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:4)
	at androidx.appcompat.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:1)
	at androidx.appcompat.widget.ActionMenuView.invokeItem(ActionMenuView.java:1)
	at androidx.appcompat.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:2)
	at android.view.View.performClick(View.java:5198)
	at android.view.View$PerformClick.run(View.java:21147)
	at android.os.Handler.handleCallback(Handler.java:739)
	at android.os.Handler.dispatchMessage(Handler.java:95)
	at android.os.Looper.loop(Looper.java:148)
	at android.app.ActivityThread.main(ActivityThread.java:5417)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)