Unexpected output: "W: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: T"

## Issue or Feature

I tried to draw a string on the canvas, but I got very weird error and program terminated immediatelly.

## Steps to Reproduce

```js
'use strict'; // Optional

var ctx = new (require('canvas').Canvas)(1, 1).getContext('2d');
ctx.font = '1px arial';
ctx.fillText('\u8081', 0, 0);
```

Nothing has been drawn to the canvas (see my comment below) and the following text has been output to the console:

```console
> node index.js
W: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: TW: T
```

Whatever is going on here, I am hundred percent sure it is not working as expected.

## Your Environment
* **Version of node-canvas:** git-master, I built it from sources
* **Environment:** node ^9.11.0 on windows 10