Fix preview button keeps loading, improvements

CHANGELOG.md

@@ -2,4 +2,4 @@
 - Switched from setuptools to hatchling for packaging.
 - Added classifiers to the package metadata.
 - Fixed "No module named 'docopt'" and "setuptools.build_meta" import errors while using .bat installer in Windows, mentioned by @nigelp in https://github.com/denizsafak/abogen/issues/2 
-- Improved code and documentation.
+- Improvements in code and documentation.

README.md

@@ -133,7 +133,7 @@ Abogen is a standalone project, but it is inspired by and shares some similariti
 - [ ] Add support for kokoro-onnx.
 - [ ] Add dark mode.
 
-# `Troubleshooting`
+## `Troubleshooting`
 If you encounter any issues while running Abogen, try launching it from the command line with:
 ```
 abogen-cli

abogen/TODO.md

@@ -1 +0,0 @@
-# Add chapter metadata for .m4a files using ffmpeg.

abogen/gui.py

@@ -1328,6 +1328,8 @@ class abogen(QWidget):
     def _play_preview_audio(self):
         temp_wav = self.preview_thread.temp_wav
         if not temp_wav:
+            self.loading_movie.stop()
+            self.btn_preview.setIcon(self.play_icon)
             self._show_error_message_box(
                 "Preview Error", "Preview error: No audio generated."
             )