Fix: wheel scroll event cause view blank.

app/pdf-viewer/buffer.py

@@ -288,6 +288,7 @@ class PdfViewerWidget(QWidget):
 
     @build_context_wrap
     def wheelEvent(self, event):
+        if not event.accept():
             self.update_scroll_offset(max(min(self.scroll_offset - self.scale * event.angleDelta().y() / 120 * self.mouse_scroll_offset, self.max_scroll_offset()), 0))
 
     def get_start_page_index(self):