fix bug where nova H-layer mass wasn't reset each timestep

src/binary_c_derivatives.h

@@ -281,6 +281,7 @@
             (STAR)->derivative[DERIVATIVE_STELLAR_MASS_NONCONSERVATIVE_LOSS] = \
             (STAR)->derivative[DERIVATIVE_STELLAR_MASS_ARTIFICIAL] =    \
             (STAR)->derivative[DERIVATIVE_STELLAR_MASS_IRRADIATIVE_LOSS] = \
+            (STAR)->derivative[DERIVATIVE_STELLAR_H_LAYER_MASS] =       \
             (STAR)->derivative[DERIVATIVE_STELLAR_MASS] =               \
             0.0;                                                        \
     }