Inline `{{if}}` helper does not re-render after condition updates to `false`

[billdami]

Given the following template:

<Label 
    text="Foo" 
    class="{{if this.someProp "color-red"}}"
/>

The Label's class will correctly change to "color-red" when this.someProp becomes true. However, if the property later changes back to false, the "color-red" class will remain, instead of being removed like it should be.