fix: use first file as epub thumbnail instead of the last. (#1111)

Author: Sola-ris

src/tagstudio/qt/previews/renderer.py

@@ -885,6 +885,7 @@ def _epub_cover(filepath: Path) -> Image.Image | None:
                         ):
                             image_data = zip_file.read(file_name)
                             im = Image.open(BytesIO(image_data))
+                            break
         except Exception as e:
             logger.error("Couldn't render thumbnail", filepath=filepath, error=type(e).__name__)