Long press on video group (by folder) crashes

Description

Performing a long press on a group of videos grouped by folder will cause a crash. This doesn't happen when grouped by name

Actual behavior

2023-05-03 16:05:22.599 7728-7728/org.videolan.vlc.debug E/VLC/VlcCrashHandler: java.lang.NullPointerException: Attempt to invoke interface method 'android.view.MenuItem android.view.MenuItem.setVisible(boolean)' on a null object reference
        at org.videolan.vlc.gui.video.VideoGridFragment.onPrepareActionMode(VideoGridFragment.kt:389)
        at androidx.appcompat.app.AppCompatDelegateImpl$ActionModeCallbackWrapperV9.onPrepareActionMode(AppCompatDelegateImpl.java:2713)
        at androidx.appcompat.view.StandaloneActionMode.invalidate(StandaloneActionMode.java:100)
        at androidx.appcompat.app.AppCompatDelegateImpl.startSupportActionModeFromWindow(AppCompatDelegateImpl.java:1337)
        at androidx.appcompat.app.AppCompatDelegateImpl.startSupportActionMode(AppCompatDelegateImpl.java:1222)
        at androidx.appcompat.app.BaseContextWrappingDelegate.startSupportActionMode(BaseContextWrappingDelegate.kt:97)
        at androidx.appcompat.app.AppCompatActivity.startSupportActionMode(AppCompatActivity.java:364)
        at org.videolan.vlc.gui.MainActivity.startSupportActionMode(MainActivity.kt:173)
        at org.videolan.vlc.gui.BaseFragment.startActionMode(BaseFragment.kt:108)
        at org.videolan.vlc.gui.video.VideoGridFragment.onLongClick(VideoGridFragment.kt:611)
        at org.videolan.vlc.gui.video.VideoGridFragment.process(VideoGridFragment.kt:579)
        at org.videolan.vlc.gui.video.VideoGridFragment.access$process(VideoGridFragment.kt:78)
        at org.videolan.vlc.gui.video.VideoGridFragment$onCreate$5.invokeSuspend(VideoGridFragment.kt:123)
        at org.videolan.vlc.gui.video.VideoGridFragment$onCreate$5.invoke(Unknown Source:8)
        at org.videolan.vlc.gui.video.VideoGridFragment$onCreate$5.invoke(Unknown Source:4)
        at kotlinx.coroutines.flow.FlowKt__TransformKt$onEach$$inlined$unsafeTransform$1$2.emit(Emitters.kt:223)
        at kotlinx.coroutines.flow.FlowKt__ChannelsKt.emitAllImpl$FlowKt__ChannelsKt(Channels.kt:62)
        at kotlinx.coroutines.flow.FlowKt__ChannelsKt.access$emitAllImpl$FlowKt__ChannelsKt(Channels.kt:1)
        at kotlinx.coroutines.flow.FlowKt__ChannelsKt$emitAllImpl$1.invokeSuspend(Unknown Source:14)
        (Coroutine boundary)
        at androidx.lifecycle.PausingDispatcherKt$whenStateAtLeast$2.invokeSuspend(PausingDispatcher.kt:162)
        at androidx.lifecycle.LifecycleCoroutineScope$launchWhenStarted$1.invokeSuspend(Lifecycle.kt:97)
        at Android.MODEL(Pixel 6a)
        at Android.VERSION(13)
        at Android.FINGERPRINT(google/bluejay/bluejay:13/TQ2A.230305.008.E1/9677224:user/release-keys)
    	Suppressed: kotlinx.coroutines.DiagnosticCoroutineContextException: [CoroutineId(21), "coroutine#21":StandaloneCoroutine{Cancelling}@85e616a, Dispatchers.Main.immediate]
    Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'android.view.MenuItem android.view.MenuItem.setVisible(boolean)' on a null object reference
        at org.videolan.vlc.gui.video.VideoGridFragment.onPrepareActionMode(VideoGridFragment.kt:389)
        at androidx.appcompat.app.AppCompatDelegateImpl$ActionModeCallbackWrapperV9.onPrepareActionMode(AppCompatDelegateImpl.java:2713)
        at androidx.appcompat.view.StandaloneActionMode.invalidate(StandaloneActionMode.java:100)
        at androidx.appcompat.app.AppCompatDelegateImpl.startSupportActionModeFromWindow(AppCompatDelegateImpl.java:1337)
        at androidx.appcompat.app.AppCompatDelegateImpl.startSupportActionMode(AppCompatDelegateImpl.java:1222)
        at androidx.appcompat.app.BaseContextWrappingDelegate.startSupportActionMode(BaseContextWrappingDelegate.kt:97)
        at androidx.appcompat.app.AppCompatActivity.startSupportActionMode(AppCompatActivity.java:364)
        at org.videolan.vlc.gui.MainActivity.startSupportActionMode(MainActivity.kt:173)
        at org.videolan.vlc.gui.BaseFragment.startActionMode(BaseFragment.kt:108)
        at org.videolan.vlc.gui.video.VideoGridFragment.onLongClick(VideoGridFragment.kt:611)
        at org.videolan.vlc.gui.video.VideoGridFragment.process(VideoGridFragment.kt:579)
        at org.videolan.vlc.gui.video.VideoGridFragment.access$process(VideoGridFragment.kt:78)
        at org.videolan.vlc.gui.video.VideoGridFragment$onCreate$5.invokeSuspend(VideoGridFragment.kt:123)

Steps to reproduce

1. Group videos by folder
2. Long press on a group

Screenshot / video

device-2023-05-03-161140

Context

App version

Master / vlc3

Android version

13

Device model

Pixel 6a

App mode

Smartphone