Fix energy min/max fields

what the title says

km3buu/tests/test_output.py

@@ -118,8 +118,8 @@ class TestGiBUUOutput(unittest.TestCase):
         np.testing.assert_array_almost_equal(rh_prob[:3], [0.0, 0.0, 0.0])
 
     def test_min_max_energy(self):
-        assert np.isnan(self.output.energy_min)
-        assert np.isnan(self.output.energy_max)
+        assert not np.isnan(self.output.energy_min)
+        assert not np.isnan(self.output.energy_max)
         np.testing.assert_array_almost_equal(self.output.energy_min, 1.0)
         np.testing.assert_array_almost_equal(self.output.energy_max, 100.0)