Error: Could not set field a on class "Class"

I'm getting an error when trying to import a class: 

```js
const imagePath = "com.fileformats.PngImage";
const ImageClass = java.import(imagePath); // error here
```
I get: 
```
Uncaught Error Error: Could not set field a on class com.fileformats.PngImage
java.lang.IllegalAccessException: Can not set static final java.lang.String field com.fileformats.PngImage.a to null value
```

