Update logic to guard against null exceptions

Author: MaggieKimani1

src/Microsoft.OpenApi.Readers/V2/OpenApiV2Deserializer.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
 using System.Collections.Generic;
@@ -113,11 +113,11 @@ public static IOpenApiAny LoadAny(ParseNode node)
 
         private static IOpenApiExtension LoadExtension(string name, ParseNode node)
         {
-            if (node.Context.ExtensionParsers.TryGetValue(name, out var parser))
+            if (node.Context.ExtensionParsers.TryGetValue(name, out var parser) && parser(
+                   OpenApiAnyConverter.GetSpecificOpenApiAny(node.CreateAny()),
+                   OpenApiSpecVersion.OpenApi2_0) is { } result)
             {
-                return parser(
-                    OpenApiAnyConverter.GetSpecificOpenApiAny(node.CreateAny()),
-                    OpenApiSpecVersion.OpenApi2_0);
+                return result;
             }
             else
             {

src/Microsoft.OpenApi.Readers/V3/OpenApiV3Deserializer.cs

@@ -171,11 +171,11 @@ public static IOpenApiAny LoadAny(ParseNode node)
 
         private static IOpenApiExtension LoadExtension(string name, ParseNode node)
         {
-            if (node.Context.ExtensionParsers.TryGetValue(name, out var parser))
+            if (node.Context.ExtensionParsers.TryGetValue(name, out var parser) && parser(
+                   OpenApiAnyConverter.GetSpecificOpenApiAny(node.CreateAny()),
+                   OpenApiSpecVersion.OpenApi3_0) is { } result)
             {
-                return parser(
-                    OpenApiAnyConverter.GetSpecificOpenApiAny(node.CreateAny()),
-                    OpenApiSpecVersion.OpenApi3_0);
+                return result;
             }
             else
             {