Apply suggestions from code review for flipped conditions.

Co-Authored-By: EraYaN <EraYaN@users.noreply.github.com>

MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs

@@ -214,7 +214,7 @@ namespace MediaBrowser.MediaEncoding.Encoder
                     throw new ArgumentNullException(nameof(path));
                 }
 
-                if (!File.Exists(path) && Directory.Exists(path))
+                if (!File.Exists(path) && !Directory.Exists(path))
                 {
                     throw new ResourceNotFoundException();
                 }