Text color incorrect in Sketch 50
Hey guys, thanks for all the awesome work!! I think I found a bug with the text color getting changed to black. I first noticed when I upgraded to Sketch 50 this morning and saw all my buttons now have black text, instead of white. I was able to reproduce the issue pretty easily using the [html-sketchapp-example](https://github.com/brainly/html-sketchapp-example) and pointing to a local server running the default page generated from [create-react-app](https://github.com/facebook/create-react-app). 

Here's what it generates, vs what is on the page:

<img width="1130" alt="screen shot 2018-05-11 at 3 17 09 pm" src="https://user-images.githubusercontent.com/125866/39945200-36127326-552f-11e8-8e69-c60955fa564b.png">

So far I've only seen it affecting text colors and it doesn't seem to matter what color, or what type of color value I use - it always turns it black.

Looking at the generated `page.asketch.json` file it seems to have the incorrect value when the asketch is being produced:

Relevant section:
```
        "name": "Welcome to React",
        "nameIsFixed": false,
        "resizingConstraint": 47,
        "resizingType": 0,
        "rotation": 0,
        "shouldBreakMaskChain": false,
        "style": {
            "color": "rgb(0, 0, 0)",
            "fontSize": 24,
            "fontFamily": "sans-serif",
            "fontWeight": 700,
            "textTransform": "none",
            "textDecoration": "none",
            "textAlign": "center"
        },
        "layers": [],
        "frame": {
            "_class": "rect",
            "constrainProportions": false,
            "height": 27,
            "width": 206.28125,
            "x": 536.859375,
            "y": 120.078125
        },
        "text": "Welcome to React",

```