Don't throw on empty URLs in clipboard

https://forums.ankiweb.net/t/dragging-and-dropping-picture-error/32313

qt/aqt/editor.py

@@ -1341,7 +1341,8 @@ class EditorWebView(AnkiWebView):
         for qurl in mime.urls():
             url = qurl.toString()
             # chrome likes to give us the URL twice with a \n
-            url = url.splitlines()[0]
+            if lines := url.splitlines():
+                url = lines[0]
                 buf += self.editor.urlToLink(url)
 
         return buf