Invalid index crash fixes

StableCollectionViewLayout/Sources/CollectionViewDataProvider.swift

@@ -20,7 +20,17 @@ public protocol CollectionViewDataProvider: AnyObject {
 
 public extension CollectionViewDataProvider {
     func isValid(indexPath: IndexPath) -> Bool {
-        numberOfSections > indexPath.section
-            && numberOfItems(inSection: indexPath.section) > indexPath.row
+        let section = indexPath.section
+        let item = indexPath.item
+
+        guard section >= 0, item >= 0 else {
+            return false
+        }
+
+        guard section < numberOfSections else {
+            return false
+        }
+
+        return item < numberOfItems(inSection: section)
     }
 }

StableCollectionViewLayout/Sources/OffsetController/OffsetControllerImpl.swift

@@ -96,7 +96,7 @@ public class OffsetControllerImpl: OffsetController {
 
         let previousVisibleFrame = previousVisibleAttributes[visibleState.targetIndexPath] ?? .zero
 
-        for item in updates {
+        for item in updates where isSane(updateItem: item) {
             visibleStateController.update(with: item)
         }
 
@@ -115,6 +115,23 @@ public class OffsetControllerImpl: OffsetController {
         return calculatedOffsetDiff
     }
 
+    private func isSane(updateItem: CollectionViewUpdateItem) -> Bool {
+        isSane(indexPath: updateItem.indexPathBeforeUpdate, isSection: updateItem.isSection)
+            && isSane(indexPath: updateItem.indexPathAfterUpdate, isSection: updateItem.isSection)
+    }
+
+    private func isSane(indexPath: IndexPath?, isSection: Bool) -> Bool {
+        guard let indexPath else {
+            return true
+        }
+
+        if isSection {
+            return indexPath.section >= 0 && indexPath.item == Int.max
+        }
+
+        return indexPath.section >= 0 && indexPath.item >= 0
+    }
+
     private func refreshVisibleState() {
         guard let collectionDataSource = collectionDataSource else {
             return