Fixed the issue where opening a random article caused the application to crash.

* The issue occurred in the Play Store variant, specifically with the copy/move functionality for ZIM files. After copying or moving a ZIM file, the application attempts to open it in the reader. However, if the application tries to open a split ZIM file with only one chunk, it throws an error indicating that the file is not a valid ZIM file (which is expected, as not all ZIM chunks have been copied/moved). When this error occurs, the menu buttons remain enabled, allowing the user to interact with them. If the user then attempts to open a random article, the application enters an infinite loop and crashes. To resolve this, we now disable the menu controls whenever an error occurs while opening a ZIM file, preventing the user from using them in such scenarios.

core/src/main/java/org/kiwix/kiwixmobile/core/main/CoreReaderFragment.kt

@@ -1735,6 +1735,10 @@ abstract class CoreReaderFragment :
         mainMenu?.onFileOpened(urlIsValid())
         setUpBookmarks(zimFileReader)
       } ?: kotlin.run {
+        // If the ZIM file is not opened properly (especially for ZIM chunks), exit the book to
+        // disable all controls for this ZIM file. This prevents potential crashes.
+        // See issue #4161 for more details.
+        exitBook()
         requireActivity().toast(R.string.error_file_invalid, Toast.LENGTH_LONG)
       }
     }