Fix focal point not saving when asset blueprint has no fields

[ncla]

Fixes #2954.

The issue was that focal point setter assumes that values will be an object.

https://github.com/ncla/cms/blob/b28df0896d614383cd0a561359d9d885cb7c00e8/resources/js/components/assets/Editor/Editor.vue#L330-L334

As far as I understood, Vue's special $set is used to trigger reactivity in a component. When the blueprint has no fields, an array is set from the HTTP response. When blueprint has fields, the response value gives us an object.

https://github.com/ncla/cms/blob/b28df0896d614383cd0a561359d9d885cb7c00e8/resources/js/components/assets/Editor/Editor.vue#L295-L298

However because values is an array now, this.$set(this.values, 'focus', point); will not work because it assumes the property in an object. If you set 2nd argument to a number then it will be used as an array index and a value will be set.

See Vue 2 docs here: https://v2.vuejs.org/v2/guide/reactivity.html#For-Objects

As a fix, I simply check if values in the HTTP response is empty to prevent changing the values type from object to array.

Side note: I initially thought that this was bug introduced with hidden fields changes but that came much later than the bug report.

[jasonvarga]

Nice one. Made a small tweak but you found the issue. 🤙 Thanks!