Don't throw if file dates cannot be modified when downloading media

Fixes #585

DiscordChatExporter.Core/Exporting/MediaDownloader.cs

@@ -45,7 +45,7 @@ namespace DiscordChatExporter.Core.Exporting
 
             Directory.CreateDirectory(_workingDirPath);
 
-            // This catches IOExceptions which is dangerous as we're working also with files
+            // This retries on IOExceptions which is dangerous as we're also working with files
             await Http.ExceptionPolicy.ExecuteAsync(async () =>
             {
                 // Download the file
@@ -56,6 +56,8 @@ namespace DiscordChatExporter.Core.Exporting
                 }
 
                 // Try to set the file date according to the last-modified header
+                try
+                {
                     var lastModified = response.Content.Headers.TryGetValue("Last-Modified")?.Pipe(s =>
                         DateTimeOffset.TryParse(s, CultureInfo.InvariantCulture, DateTimeStyles.None, out var date)
                             ? date
@@ -68,6 +70,14 @@ namespace DiscordChatExporter.Core.Exporting
                         File.SetLastWriteTimeUtc(filePath, lastModified.Value.UtcDateTime);
                         File.SetLastAccessTimeUtc(filePath, lastModified.Value.UtcDateTime);
                     }
+                }
+                catch
+                {
+                    // This can apparently fail for some reason.
+                    // https://github.com/Tyrrrz/DiscordChatExporter/issues/585
+                    // Updating file dates is not a critical task, so we'll just
+                    // ignore exceptions thrown here.
+                }
             });
 
             return _pathCache[url] = filePath;