[BUG] Null Reference Exception when using --model-name-suffix for fsharp-giraffe-server generator

Created by: HerrNiklasRaab

When running this commande openapi-generator generate -i api.yml -g fsharp-giraffe-server --dry-run --model-name-suffix "Dto" I get the following exception:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.util.Map.put(Object, Object)" because "models" is null
        at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:512)
        at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:875)
        at org.openapitools.codegen.cmd.Generate.execute(Generate.java:441)
        at org.openapitools.codegen.cmd.OpenApiGeneratorCommand.run(OpenApiGeneratorCommand.java:32)
        at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:66)

When I run it with any other generator, I don't get the exception: openapi-generator generate -i api.yml -g aspnetcore --dry-run --model-name-suffix "Dto"

When I run it without --model-name-suffix, I don't get the exception: openapi-generator generate -i api.yml -g fsharp-giraffe-server --dry-run

@nmfisher Could it be that this option is not supported yet for the F# generator?