@Test
public void protonsDontCauseNPE() throws Exception {

    IAtomContainer proton = new AtomContainer(1, 0, 0, 0);
    proton.addAtom(atom("H", +1, 0));
    CircularFingerprinter circ = new CircularFingerprinter(CircularFingerprinter.CLASS_FCFP2);
    assertThat(circ.getBitFingerprint(proton).cardinality(), is(0));
}