Method JLayer.remove((Component) null) throws NPE (see CR#6875173)
but if glassPane is set to null and view is not null then NPE isn't thrown:

import javax.swing.*;
import java.awt.*;

public class NPE {
    public static void main(String[] args) {
        JLayer<Component> layer = new JLayer<Component>(new Component(){});
        // comment the following line to get NPE
        layer.setGlassPane(null);
        // NPE might or might not be thrown
        layer.remove((Component)null);
    }
}

Behavior should be unified.
The following JCK test verifies NPE throwing:
api/javax_swing/JLayer/index.html#General[remove_nullComponent_01]
api/javax_swing/JLayer/index.html#General[remove_nullComponent_02]
api/javax_swing/JLayer/index.html#General[remove_nullComponent_03]