GEAR : fix the SN energy when the stars must not do feedback

This MR implements a minor fix to prevent stars from injecting energy if mass_ejected > sp->mass. In such cases, the ejected mass and SN II and Ia number were set to 0, but not the energy. Thus, in runner_iact_nonsym_feedback_apply(), we could still inject energy and metal mass.

Now, the energy is correctly set to 0, so we don't do feedback as expected.