Fix file deletion

CHDataManagement/Model/Page.swift

@@ -156,6 +156,14 @@ final class Page: Item {
     func hasContent(in language: ContentLanguage) -> Bool {
         content.storage.hasPageContent(for: id, language: language)
     }
+
+    func remove(_ file: FileResource) {
+        if requiredFiles.contains(file) {
+            requiredFiles.remove(file)
+        }
+        english.remove(linkPreviewImage: file)
+        german.remove(linkPreviewImage: file)
+    }
 }
 
 extension Page: DateItem {