         let delta = abs(preheatRect.midY - self.previousPreheatRect.midY)
         guard delta > view.bounds.height / 3 else { return }
         
-        let group = self.imagePickerController.groupDataManager.fetchGroup(with: selectedGroupId)
+        guard let group = self.imagePickerController.groupDataManager.fetchGroup(with: selectedGroupId) else {
+            assertionFailure("Expect group")
+            return
+        }
         
         // Compute the assets to start caching and to stop caching.
         let (addedRects, removedRects) = self.differencesBetweenRects(self.previousPreheatRect, preheatRect)

        }
        assetIndex = (index - (self.hidesCamera ? 0 : 1))
        
        let group = self.imagePickerController.groupDataManager.fetchGroup(with: selectedGroupId)
        return self.imagePickerController.groupDataManager.fetchAsset(group, index: assetIndex)
    }
    

	open func updateTitleView() {
        guard let selectedGroupId = self.selectedGroupId else { return }
        
        guard let group = self.imagePickerController.groupDataManager.fetchGroup(with: selectedGroupId) else {
            assertionFailure("Expect group")
            return
        }
		self.title = group.groupName
		
		let groupsCount = self.imagePickerController.groupDataManager.groupIds?.count ?? 0
