Animation trigger with params won't work without a value

[jpzwarte]

[ ] Regression (a behavior that used to work and stopped working in a new release)
[x] Bug report  
[ ] Performance issue
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question
[ ] Other... Please describe:

So i have the following template:

    <div *ngFor="let image of chapterImages | async"
         [@image]="chapterAnimation">...</div>

And in the component:

  animations: [
    trigger('image', [
      transition(':enter', [
        style({ transform: 'translateX({{enter}})' }),
        animate('0.7s ease-in-out', style({ transform: 'translateX(0)' }))
      ], { params: { enter: '0%' } }),
      transition(':leave', [
        style({ transform: 'translateX(0)' }),
        animate('0.7s ease-in-out', style({ transform: 'translateX({{leave}})' }))
      ], { params: { leave: '-100%' } })
    ])
  ]

  chapterAnimation = {
    value: 'foo',
    params: {
      enter: '100%',
      leave: '-100%'
    }
  };

If i leave out the value: 'foo' line, the animation WILL NOT use the provided params and just use the default params. That is the bug (took me quite a while to figure out).

Angular 6.0.7

[jpzwarte]

cc @matsko