Generated C# POCOs throw a NRE when a collection property is null

Description

C# POCOs with collection properties throw a NullReferenceException when the collection property is null and the #Equals() method of the generated POCO is called.

public bool Equals(CommentDTO input)
{
	if (input == null)
		return false;

	return
		(
			this.Editors == input.Editors ||
			this.Editors != null &&
			this.Editors.SequenceEqual(input.Editors)
		);
}

So when I have two CommentDTO instances and call c1.Equals(c2), a NRE is thrown when c2 hasn't any editors set (since input.Editors is null).

Example test:

[Test]
public void Test() {
  CommentDTO c1 = new CommentDTO { Editors = new List<EditorDTO> { new EditorDTO() } };
  CommentDTO c2 = new CommentDTO();

 Assert.IsFalse(c1.Equals(c2));
}

Swagger-codegen version

2.3.1

Swagger declaration file content or url

Not specific to my API, but there you go: https://gist.github.com/molehillrocker/cc9d0ea54f3cb720c1e7726185c5c483

Command line used for generation

$java -jar swagger-codegen-cli.jar generate -i <url> -l csharp -o .\

Suggest a fix/enhancement

Either guard the check inside the #Equals() method or initialize all collection properties with an empty list/collection.

Start by tracing the generated C# POCO Equals method shown in the issue and reproduce it with the provided CommentDTO test and Swagger declaration. Generate the C# client with the stated swagger-codegen command, then verify that comparing objects with a null collection no longer throws and the assertion passes.