Merge pull request #498 from microsoft/dm/fixwalker

Fixes to OpenApiWalker

Author: darrelmiller

src/Microsoft.OpenApi/Services/OpenApiWalker.cs

@@ -732,6 +732,11 @@ internal void Walk(OpenApiEncoding encoding)
             }
 
             _visitor.Visit(encoding);
+
+            if (encoding.Headers != null)
+            {
+                Walk(encoding.Headers);
+            }
             Walk(encoding as IOpenApiExtensible);
         }
 
@@ -787,6 +792,11 @@ internal void Walk(OpenApiSchema schema, bool isComponent = false)
                 });
             }
 
+            if (schema.AdditionalProperties != null)
+            {
+                Walk("additionalProperties", () => Walk(schema.AdditionalProperties));
+            }
+
             Walk(OpenApiConstants.ExternalDocs, () => Walk(schema.ExternalDocs));
 
             Walk(schema as IOpenApiExtensible);