chore: clean up

Author: MaggieKimani1

src/Microsoft.OpenApi/Models/OpenApiReference.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license.
 
 using System;
+using System.Linq;
 using System.Text.Json.Nodes;
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Interfaces;

src/Microsoft.OpenApi/Reader/V31/OpenApiSchemaDeserializer.cs

@@ -399,10 +399,10 @@ public static IOpenApiSchema LoadSchema(ParseNode node, OpenApiDocument hostDocu
                 schema.Extensions.Remove(OpenApiConstants.NullableExtension);
             }
 
-            if (identifier is not null && hostDocument.Workspace is not null)
+            if (!string.IsNullOrEmpty(identifier) && hostDocument.Workspace is not null)
             {
                 // register the schema in our registry using the identifier's URL
-                hostDocument.Workspace.RegisterComponentForDocument(hostDocument, schema, identifier);
+                hostDocument.Workspace.RegisterComponentForDocument(hostDocument, schema, identifier!);
             }
 
             return schema;