[Swift3] Illegal enum value null for parameter type integer

[Swift3]

Description

"Parameter Object" with integer type and enum collection with 0 generates an error:

[main] WARN io.swagger.models.parameters.AbstractSerializableParameter - Illegal enum value null for parameter type integer

Swagger-codegen version

2.2.2

Swagger declaration file content or url

"filter_type": {
    "description": "0=NONE,1=TYPE_1,2=TYPE_2,3=TYPE_3",
    "type": "integer",
    "enum": [
        0,
        1,
        2,
        3
    ]
},

Command line used for generation

java -jar shared/swagger-codegen-cli.jar generate -i etc/swagger/swagger.json -l swift3 -o shared/swift_client

Run the stated Java command with etc/swagger/swagger.json and inspect the generated output in shared/swift_client. Start by tracing how the Swift3 generator handles the integer enum containing 0; done means generation no longer emits the illegal enum value null warning and the enum values are preserved.