check if arg1 free rules with goto cleanup in assignToBundleMember

[ramagottfried]

free_arg1 should probably be initialized higher in the function --> https://github.com/CNMAT/libo/blob/master/osc_expr.c#L1853

but it's not clear to me yet, when arg1 should be freed as an atom_array

    cleanup:
        if(arg1 && free_arg1){
            osc_atom_array_u_free(arg1);
        }

[maccallum]

This is ok