Fixed instantiation of Components in V2 deserializer

Author: darrelmiller

src/Microsoft.OpenApi.Readers/V2/OpenApiDocumentDeserializer.cs

@@ -45,10 +45,13 @@ internal static partial class OpenApiV2Deserializer
             {"paths", (o, n) => o.Paths = LoadPaths(n)},
             {
                 "definitions",
-                (o, n) => o.Components.Schemas = n.CreateMapWithReference(
+                (o, n) => {
+                    o.Components = new OpenApiComponents();
+                    o.Components.Schemas = n.CreateMapWithReference(
                     ReferenceType.Schema,
                     "#/definitions/",
-                    LoadSchema)
+                    LoadSchema);
+                    }
             },
             {
                 "parameters",

src/Microsoft.OpenApi/Models/OpenApiDocument.cs

@@ -41,7 +41,7 @@ public class OpenApiDocument : IOpenApiSerializable, IOpenApiExtensible
         /// <summary>
         /// An element to hold various schemas for the specification.
         /// </summary>
-        public OpenApiComponents Components { get; set; } = new OpenApiComponents();
+        public OpenApiComponents Components { get; set; }
 
         /// <summary>
         /// A declaration of which security mechanisms can be used across the API.

test/Microsoft.OpenApi.Readers.Tests/V2Tests/ComparisonTests.cs

@@ -18,7 +18,7 @@ public class ComparisonTests
         [Theory]
         [InlineData("minimal")]
         [InlineData("basic")]
-      //  [InlineData("definitions")]  Currently broken due to V3 references not behaving the same as V2
+        //[InlineData("definitions")]  //Currently broken due to V3 references not behaving the same as V2
         public void EquivalentV2AndV3DocumentsShouldProductEquivalentObjects(string fileName)
         {
             using (var streamV2 = File.OpenRead(Path.Combine(SampleFolderPath, $"{fileName}.v2.yaml")))