Unable to Preview Other Files after Previewing an ePub

[shijie.chen]

Title: Unable to Preview Other Files after Previewing an ePub

Describe the bug
After previewing an ePub file, the program enters into a state of "waiting", preventing the user from previewing any other files.

To Reproduce
Steps to reproduce the behaviour:

1. Open the application.
2. Navigate to an ePub file.
3. Click on the file to start preview.
4. During the "waiting" state after the preview, attempt to preview another file.
5. Notice that you are unable to preview any other files.

Expected behavior
The user should be able to preview other files after previewing an ePub file, regardless of the "waiting" state.