Fix chapters grid view

app/src/main/kotlin/org/koitharu/kotatsu/details/ui/adapter/ChapterGridItemAD.kt

@@ -24,7 +24,7 @@ fun chapterGridItemAD(
 
 	bind { payloads ->
 		if (payloads.isEmpty()) {
-			binding.textViewTitle.text = item.chapter.formatNumber()
+			binding.textViewTitle.text = item.chapter.formatNumber() ?: "?"
 		}
 		binding.imageViewNew.isVisible = item.isNew
 		binding.imageViewCurrent.isVisible = item.isCurrent

app/src/main/kotlin/org/koitharu/kotatsu/details/ui/pager/chapters/ChapterGridSpanHelper.kt

@@ -4,6 +4,7 @@ import android.view.View
 import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import org.koitharu.kotatsu.R
+import org.koitharu.kotatsu.list.ui.adapter.ListItemType
 import kotlin.math.roundToInt
 
 class ChapterGridSpanHelper private constructor() : View.OnLayoutChangeListener {
@@ -29,6 +30,22 @@ class ChapterGridSpanHelper private constructor() : View.OnLayoutChangeListener
 		(rv.layoutManager as? GridLayoutManager)?.spanCount = getSpanCount(rv)
 	}
 
+	class SpanSizeLookup(
+		private val recyclerView: RecyclerView
+	) : GridLayoutManager.SpanSizeLookup() {
+
+		override fun getSpanSize(position: Int): Int {
+			return when (recyclerView.adapter?.getItemViewType(position)) {
+				ListItemType.CHAPTER_LIST.ordinal, // for smooth transition
+				ListItemType.HEADER.ordinal -> getTotalSpans()
+
+				else -> 1
+			}
+		}
+
+		private fun getTotalSpans() = (recyclerView.layoutManager as? GridLayoutManager)?.spanCount ?: 1
+	}
+
 	companion object {
 
 		fun attach(view: RecyclerView) {

app/src/main/kotlin/org/koitharu/kotatsu/details/ui/pager/chapters/ChaptersFragment.kt

@@ -66,7 +66,9 @@ class ChaptersFragment :
 		)
 		viewModel.isChaptersInGridView.observe(viewLifecycleOwner) { chaptersInGridView ->
 			binding.recyclerViewChapters.layoutManager = if (chaptersInGridView) {
-				GridLayoutManager(context, ChapterGridSpanHelper.getSpanCount(binding.recyclerViewChapters))
+				GridLayoutManager(context, ChapterGridSpanHelper.getSpanCount(binding.recyclerViewChapters)).apply {
+					spanSizeLookup = ChapterGridSpanHelper.SpanSizeLookup(binding.recyclerViewChapters)
+				}
 			} else {
 				LinearLayoutManager(context)
 			}

app/src/main/kotlin/org/koitharu/kotatsu/list/ui/adapter/TypedListSpacingDecoration.kt

@@ -86,4 +86,5 @@ class TypedListSpacingDecoration(
 		|| this == ListItemType.FILTER_SORT
 		|| this == ListItemType.FILTER_TAG
 		|| this == ListItemType.CHAPTER_LIST
+		|| this == ListItemType.CHAPTER_GRID
 }

app/src/main/kotlin/org/koitharu/kotatsu/reader/ui/ChaptersSheet.kt

@@ -93,7 +93,9 @@ class ChaptersSheet : BaseAdaptiveSheet<SheetChaptersBinding>(),
 		}
 		ChapterGridSpanHelper.attach(binding.recyclerView)
 		binding.recyclerView.layoutManager = if (settings.isChaptersGridView) {
-			GridLayoutManager(context, ChapterGridSpanHelper.getSpanCount(binding.recyclerView))
+			GridLayoutManager(context, ChapterGridSpanHelper.getSpanCount(binding.recyclerView)).apply {
+				spanSizeLookup = ChapterGridSpanHelper.SpanSizeLookup(binding.recyclerView)
+			}
 		} else {
 			LinearLayoutManager(context)
 		}