Fix stale state of the shortcut slot tab a11y content description

This is due to that we don't assign a none string when there's no
affordaces selected.

Test: Manually tested that it annouces none when none is selected
Bug: 280551132
Flag: None
Change-Id: Ic474c8ff6941efb4ab24aa507e9e77de360d2ba7
diff --git a/src/com/android/customization/picker/quickaffordance/ui/adapter/SlotTabAdapter.kt b/src/com/android/customization/picker/quickaffordance/ui/adapter/SlotTabAdapter.kt
index 8891b03..0e3b716 100644
--- a/src/com/android/customization/picker/quickaffordance/ui/adapter/SlotTabAdapter.kt
+++ b/src/com/android/customization/picker/quickaffordance/ui/adapter/SlotTabAdapter.kt
@@ -67,7 +67,9 @@
                 .find { it.isSelected.value }
                 ?.text
                 ?.asString(holder.itemView.context)
-        stateDescription?.let { holder.itemView.stateDescription = it }
+        holder.itemView.stateDescription =
+            stateDescription
+                ?: holder.itemView.resources.getString(R.string.keyguard_affordance_none)
     }
 
     class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {