[twitter] fix potential 'UnboundLocalError' (#7932)

this happens with Tweets containing both images and video
when 'videos' are disabled.

gallery_dl/extractor/twitter.py

@@ -217,6 +217,8 @@ class TwitterExtractor(Extractor):
                         "duration": video_info.get(
                             "duration_millis", 0) / 1000,
                     }
+                else:
+                    continue
             elif "media_url_https" in media:
                 url = media["media_url_https"]
                 if url[-4] == ".":

test/results/twitter.py

@@ -349,6 +349,27 @@ __tests__ = (
     "type": "video",
 },
 
+{
+    "#url"     : "https://x.com/carrotsprout_/status/1577924293023133696",
+    "#comment" : "mixed image & video",
+    "#class"   : twitter.TwitterTweetExtractor,
+    "#results" : (
+        "https://pbs.twimg.com/media/FeXpxOyaYAA9L88?format=jpg&name=orig",
+        "https://video.twimg.com/ext_tw_video/1577924276447248386/pu/vid/720x800/kNsjUvJ5knrSx5WM.mp4?tag=12",
+    ),
+},
+
+{
+    "#url"     : "https://x.com/gopherfootball/status/1950259395432239395",
+    "#comment" : "mixed images & video; 'videos' disabled (#7932)",
+    "#class"   : twitter.TwitterTweetExtractor,
+    "#options" : {"videos": False},
+    "#results" : (
+        "https://pbs.twimg.com/media/GxC2eRJWAAAH_NM?format=jpg&name=orig",
+        "https://pbs.twimg.com/media/GxC2eRAWoAA8gGQ?format=jpg&name=orig",
+    ),
+},
+
 {
     "#url"     : "https://twitter.com/playpokemon/status/1263832915173048321/",
     "#comment" : "content with emoji, newlines, hashtags (#338)",