fix test with missing docset.yml

Author: Mpdreamz

src/Elastic.Markdown/IO/ConfigurationFile.cs

@@ -49,7 +49,10 @@ public ConfigurationFile(IFileInfo sourceFile, IDirectoryInfo rootPath, BuildCon
 		yaml.Load(textReader);
 
 		if (yaml.Documents.Count == 0)
+		{
 			context.EmitWarning(sourceFile, "empty configuration");
+			return;
+		}
 
 		// Examine the stream
 		var mapping = (YamlMappingNode)yaml.Documents[0].RootNode;

tests/Elastic.Markdown.Tests/OutputDirectoryTests.cs

@@ -18,6 +18,7 @@ public async Task CreatesDefaultOutputDirectory()
 		var logger = new TestLoggerFactory(output);
 		var fileSystem = new MockFileSystem(new Dictionary<string, MockFileData>
 		{
+			{ "docs/source/docset.yml", new MockFileData("") },
 			{ "docs/source/index.md", new MockFileData("test") }
 		}, new MockFileSystemOptions
 		{