Fix NullReferenceException error for pathless files

When the new VS Text Editor is opened with some special output
(e.g. Stack Trace Explorer in ReSharper), it has no path, so the
argument `path` is null, and NullReferenceException is thrown in
parser.Parse(string). So null-check must be needed.

Author: takeshik

src/EditorConfig.VisualStudio/Helpers/SettingsExtensions.cs

@@ -11,6 +11,7 @@ internal static class ConfigLoader
         public static bool TryLoad(string path, out FileConfiguration fileConfiguration)
         {
             fileConfiguration = null;
+            if (string.IsNullOrEmpty(path)) return false;
             var parser = new EditorConfigParser();
             var configurations = parser.Parse(path);
             if (!configurations.Any()) return false;