[BUG] can't override model.mustache, api.mustache

Description

The bug occurs when I provide a template folder for the generator, with model.mustache in it.
Instead of generating output, the tool just generates a stacktrace.

Looks like the problem doesn't happen if I replace other templates. Only models.mustache.

openapi-generator version

I used the docker-based openapi-generator-cli version 4.0.0-SNAPSHOT
I was trying to generate typescript-jquery output
I am using windows 10

OpenAPI declaration file content or url

The attached zip contains an OAS3 file sufficient to reproduce the bug
demo.zip

Command line used for generation

After setting everything up as described in steps to reproduce
docker run --rm -v "/tmp:/local" openapitools/openapi-generator-cli generate -i /local/demo.yaml -t /local/templates_folder -g typescript-jquery -o /local/output

Steps to reproduce

1. download the openapi-generator tool
2. create an empty /tmp/templates_folder
3. copy the file openapi-generator-master\modules\openapi-generator\src\main\resources\typescript-jquery\model.mustache to /tmp/templates_folder
4. create a demo.yaml file as described above, and put it in /tmp
5. Run code generation using the OAS file and the themplates_folder
   docker run --rm -v "/tmp:/local" openapitools/openapi-generator-cli generate -i /local/demo.yaml -t /local/templates_folder -g typescript-jquery -o /local/output

expected: since everything is standard and we are using standard templates, we expect to get the generated output.
Instead, we get a stacktrace, and error messages about the template not being found

Start with the typescript-jquery generator and the custom /tmp/templates_folder containing model.mustache, then run the Docker command from the report against the attached demo.yaml. Compare the model.mustache override with the other template overrides and confirm that generation completes without the reported stacktrace when the standard template is copied into the custom folder.