UIButton nullpointer

I’m trying to use a couple of UIButtons as a test, but when I try to run the following, it throws a Nullpointer

UIButton _button = new UIButton(name, x, y, w, h, new InputHandler(),  new UIColorScheme(), UIButton.BORDER | UIButton.DRAW_DOWN | UIButton.DRAW_OVER);

The error is

Could not load image...  URL was null.
Could not load image...  URL was null.
        at com.jme.ui.UIText.<init>(Unknown Source)
        at com.jme.ui.UIText.<init>(Unknown Source)
        at com.jme.ui.UIButton.setText(Unknown Source)
        at EnvDev.createUIButton(EnvDev.java:125)
        at EnvDev.attachEditBar(EnvDev.java:89)
        at EnvDev.initGame(EnvDev.java:184)
        at com.jme.app.BaseGame.start(Unknown Source)
        at EnvDev.main(EnvDev.java:275)

I'm not sure where the "Could not load image" is coming from. Anyone have any idea as to what causes this?

You should specify the textures you want the button to be drawn by - use the other constructor.