NullpointerException in mavan code generation when certification validation is disabled

Hi

I am using the following plugin for the code generation for my openAPI spec 3.0

io.swagger.codegen.v3
swagger-codegen-maven-plugin

In the plugin configuration i have set the following property to true

<environmentVariables>
<io.swagger.v3.parser.util.RemoteUrl.trustAll>true</io.swagger.v3.parser.util.RemoteUrl.trustAll>
</environmentVariables>

schema:
$ref: 'https://myswaggerhubdomain/v1/domains/Global_Domains/V0/#/responses/ErrorResponse'

But the parser throwing the NullpointerException as follows. Could you please advise what could be the problem ?

java.lang.NullPointerException at io.swagger.v3.parser.util.OpenAPIDeserializer.getSchema(OpenAPIDeserializer.java:2438) at io.swagger.v3.parser.ResolverCache.loadRef(ResolverCache.java:152) at io.swagger.v3.parser.processors.ExternalRefProcessor.processRefToExternalSchema(ExternalRefProcessor.java:56) at io.swagger.v3.parser.processors.SchemaProcessor.processReferenceSchema(SchemaProcessor.java:214) at io.swagger.v3.parser.processors.SchemaProcessor.processSchema(SchemaProcessor.java:37) at io.swagger.v3.parser.processors.ResponseProcessor.processResponse(ResponseProcessor.java:52) at io.swagger.v3.parser.processors.OperationProcessor.processOperation(OperationProcessor.java:67) at io.swagger.v3.parser.processors.PathsProcessor.processPaths(PathsProcessor.java:84) at io.swagger.v3.parser.OpenAPIResolver.resolve(OpenAPIResolver.java:49) at io.swagger.v3.parser.OpenAPIV3Parser.readLocation(OpenAPIV3Parser.java:67) at io.swagger.parser.OpenAPIParser.readLocation(OpenAPIParser.java:16) at io.swagger.codegen.v3.config.CodegenConfigurator.toClientOptInput(CodegenConfigurator.java:517) at io.swagger.codegen.v3.maven.plugin.CodeGenMojo.execute(CodeGenMojo.java:525)

Start by reproducing the supplied Maven configuration and external $ref, then inspect io.swagger.v3.parser.util.OpenAPIDeserializer.getSchema at line 2438 and follow the call through ResolverCache.loadRef. Compare the parser state for the referenced response with the stack trace to identify why it becomes null. Done means the case is understood and the parser no longer fails with an unexplained NullPointerException.