You will need to Clamp the output of the Noise to 0 to 1 (though you could also set the minimum Output to 0 as well). You will probably also need to add some smoothing through the Filterwidth and adjust your scale to way way below 1 (like 0.0575 gave me a good result). The Levels in the noise node refers to the levels of noise that the module is mixing to generate a noise field.