[YoutubeDL] check annotations availabilty(closes #18582)

youtube_dl/YoutubeDL.py

@@ -1783,6 +1783,8 @@ class YoutubeDL(object):
             annofn = replace_extension(filename, 'annotations.xml', info_dict.get('ext'))
             if self.params.get('nooverwrites', False) and os.path.exists(encodeFilename(annofn)):
                 self.to_screen('[info] Video annotations are already present')
+            elif not info_dict.get('annotations'):
+                self.report_warning('There are no annotations to write.')
             else:
                 try:
                     self.to_screen('[info] Writing video annotations to: ' + annofn)