[zerochan] fix "KeyError: 'author'" (#7282)

fixes regression introduced in d746e025a0

gallery_dl/extractor/zerochan.py

@@ -74,7 +74,6 @@ class ZerochanExtractor(BooruExtractor):
         extr = text.extract_from(page)
         data = {
             "id"      : text.parse_int(entry_id),
-            "author"  : jsonld["author"]["name"],
             "file_url": jsonld["contentUrl"],
             "date"    : text.parse_datetime(jsonld["datePublished"]),
             "width"   : text.parse_int(jsonld["width"][:-3]),
@@ -88,6 +87,11 @@ class ZerochanExtractor(BooruExtractor):
                 'id="source-url"', '</p>').rpartition("</s>")[2])),
         }
 
+        try:
+            data["author"] = jsonld["author"]["name"]
+        except Exception:
+            data["author"] = ""
+
         html = data["tags"]
         tags = data["tags"] = []
         for tag in html.split("<li class=")[1:]: