TikTok: Document profile avatar limitation

docs/supportedsites.md

@@ -929,7 +929,7 @@ Consider all listed sites to potentially be NSFW.
 <tr>
     <td>TikTok</td>
     <td>https://www.tiktok.com/</td>
-    <td>Photos, Videos, Audio, User Profiles, Profile Avatars<br><br><b>Videos, Audio, and User Profiles require yt-dlp or youtube-dl.</b> Pass <code>-o videos</code> to download photos only, and <code>-o tiktok-range="a-yt-dlp-range"</code> to tell yt-dlp to only extract XYZ links when scraping a user profile.</td>
+    <td>Photos, Videos, Audio, User Profiles, Profile Avatars<br><br><b>Videos, Audio, and User Profiles require yt-dlp or youtube-dl.</b> Pass <code>-o videos</code> to download photos only, and <code>-o tiktok-range="a-yt-dlp-range"</code> to tell yt-dlp to only extract XYZ links when scraping a user profile. Also note that profile avatars will only be downloaded when downloading a User Profile and if the user has at least one post.</td>
     <td><a href="https://github.com/mikf/gallery-dl#cookies">Cookies</a></td>
 </tr>
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