Return None if no text in xml, due to no subtitle and automatic_captions with gibberish except xml(xml format text part is empty) in this video https://youtu.be/LI0mzC6sl7w

fetchYoutubeSubtitle.py

@@ -227,6 +227,8 @@ def xml_caption_to_srt(xml_captions: str) -> str:
         caption = unescape(
             text.replace("\n", " ").replace("  ", " "),
         )
+        if len(caption) == 0:
+            continue
         try:
             duration = float(child.attrib["dur"])
         except KeyError:
@@ -241,7 +243,8 @@ def xml_caption_to_srt(xml_captions: str) -> str:
             text=caption,
         )
         segments.append(line)
-    return "\n".join(segments).strip()
+    # return None if no text in xml
+    return "\n".join(segments).strip() if len(segments) > 0 else None
 
 
 async def fetchSubtitleUrls(url: str, proxy: Optional[str] = None) -> json: