Uncaught Error: Cant access the filesystem

# Expected Behavior

Jim.read() to read the file
lenna.write('lena-small-bw.jpg') to write a file to the local folder.

# Current Behavior

Jim.read() works fine.
lenna.write('lena-small-bw.jpg') throws an error

# Failure Information (for bugs)

index.js:139 Error: Cant access the filesystem. You can use the getBase64 method.
at Jimp.write (jimp.js:33813)
at index.js:132

## Steps to Reproduce

the codes:
Jimp.read('static/images/beach.jpg')
.then(lenna => {
console.log('lenna', lenna)
return lenna
.resize(120, 120) // resize
.quality(60) // set JPEG quality
.greyscale() // set greyscale
.write('lena-small-bw.jpg');
.catch(err => {
console.error(err);
});

- Jimp Version: "jimp": "^0.6.4"
- Operating System: ubuntu 16.04
- Node version: v11.4.0