GetModel is not generated for getCollection if getEntity is not using `json` representation

[mnembrini]

Describe the bug

When GET_COLLECTION is present with a json representatino but GET_ENTITY is not using json representation, then
the Model class is not generated, but it is needed.

To Reproduce
Steps to reproduce the behavior:
Check out branch /bug/missing_model and gradle clean generateRestArtifacts compileJava. Note the compilation error due to the missing Model class

Expected behavior
The Model class is generated

[saw303]

@mnembrini new version available 2.3.13

[mnembrini]

This is still a problem in 2.3.16