Only include extensions in JSON if populated

Author: tvernum

x-pack/plugin/identity-provider/src/main/java/org/elasticsearch/xpack/idp/saml/sp/SamlServiceProviderDocument.java

@@ -538,7 +538,9 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         builder.field(Fields.Attributes.EMAIL.getPreferredName(), attributeNames.email);
         builder.field(Fields.Attributes.NAME.getPreferredName(), attributeNames.name);
         builder.field(Fields.Attributes.ROLES.getPreferredName(), attributeNames.roles);
-        builder.field(Fields.Attributes.EXTENSIONS.getPreferredName(), attributeNames.extensions);
+        if (attributeNames.extensions != null && attributeNames.extensions.isEmpty() == false) {
+            builder.field(Fields.Attributes.EXTENSIONS.getPreferredName(), attributeNames.extensions);
+        }
         builder.endObject();
 
         builder.startObject(Fields.CERTIFICATES.getPreferredName());