Two consecutive commas generated with nav schematics

[klemenoslaj]

Bug, feature request, or proposal:

Bug

What is the expected behavior?

Generating nav using material schematics should generate valid TypeScript code.

What is the current behavior?

When generating the nav with OnPush changeDetection we get two consecutive commas.

What are the steps to reproduce?

Execute the following command in Angular workspace:

ng generate @angular/material:nav navigation --project myProject --changeDetection=OnPush

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Angular CLI: 7.1.0
Node: 10.13.0
OS: darwin x64
Angular: 7.1.0
... animations, bazel, common, compiler, compiler-cli, core
... elements, forms, http, platform-browser
... platform-browser-dynamic, platform-server, router

Package Version

@angular-devkit/architect 0.10.6
@angular-devkit/core 7.0.6
@angular-devkit/schematics 7.0.6
@schematics/angular 7.0.6
@schematics/update 0.11.0 (cli-only)
rxjs 6.3.3
typescript 3.1.1

Is there anything else we should know?

I would be filling to submit my first pull request to fix this issue.

[devversion]

@klemenoslaj Please feel free to do. Otherwise I can just take care of it. Also have a look for the other schematics as those can have the same problem.

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