fix: missing null prop operator on parameter reference

Signed-off-by: Vincent Biret <[email protected]>

Author: baywet

src/Microsoft.OpenApi/Models/References/OpenApiParameterReference.cs

@@ -40,7 +40,7 @@ internal OpenApiParameterReference(OpenApiParameter target, string referenceId):
         }
 
         /// <inheritdoc/>
-        public string Name { get => Target.Name; }
+        public string Name { get => Target?.Name; }
 
         /// <inheritdoc/>
         public string Description
@@ -86,10 +86,10 @@ public string Description
         public bool Explode { get => Target?.Explode ?? default; }
 
         /// <inheritdoc/>
-        public IDictionary<string, OpenApiMediaType> Content { get => Target.Content; }
+        public IDictionary<string, OpenApiMediaType> Content { get => Target?.Content; }
 
         /// <inheritdoc/>
-        public IDictionary<string, IOpenApiExtension> Extensions { get => Target.Extensions; }
+        public IDictionary<string, IOpenApiExtension> Extensions { get => Target?.Extensions; }
 
         /// <inheritdoc/>
         public override IOpenApiParameter CopyReferenceAsTargetElementWithOverrides(IOpenApiParameter source)