Gradient: set from, to not working
I tested the folowing code on a simple rectangle shape layer. Setting the gradient.to.x also changes the gradient.from.y which is not the behavior which I would expect. I think there is a bug here. 

https://developer.sketchapp.com/reference/api/#gradient 
```
let document = require('sketch/dom').getSelectedDocument();
let selection = document.selectedLayers;

selection.layers[0].style.fills[0].fill = 'Gradient';
selection.layers[0].style.fills[0].gradient.gradientType = 'Radial';
selection.layers[0].style.fills[0].gradient.stops = [{
            position: 0,
            color: '#c0ffee',
        },
        {
            position: 0.5,
            color: '#0ff1ce',
        },
        {
            position: 1,
            color: '#bada55',
        },
    ];
// selection.layers[0].style.fills[0].gradient.from.x = 0.5;
// selection.layers[0].style.fills[0].gradient.from.y = 0;
selection.layers[0].style.fills[0].gradient.to.x = 0.5;
// selection.layers[0].style.fills[0].gradient.to.y = 1;

console.log(selection.layers[0].style.fills[0].gradient);
```
