updateEnergyContributions calculation typo

[MessiXiang]

Describe the bug

In file basilisk/src/simulation/dynamics/_GeneralModuleFiles/gravityEffector.cpp, function updateEnergyContributions calculates the potential energy contribution. But in line 299, there's probably a typo.

if (this->centralBody && !body->isCentralBody) // If there is a central body and it's not
                                                       // 'body'
{
    // potential of central body w/in current planet field. leads to
    // relative potential energy solution
    orbPotEnergyContr += body->gravityModel->computePotentialEnergy(r_PN_N - r_CN_N);
}
orbPotEnergyContr = body->gravityModel->computePotentialEnergy(
    r_cP_N); // Potential w/in current planet field

As shown above, the orbPotEnergyContr need to add all these energy up. However, it was given by body->gravityModel->computePotentialEnergy(r_cP_N) at last, which supposed to be +=

To reproduce

see above

Expected behavior

orbPotEnergyContr += body->gravityModel->computePotentialEnergy(
    r_cP_N); // Potential w/in current planet field

commit:
2b4dfec

[schaubh]

I agree something is odd here. I will have to find some time to look at this much more carefully. Thanks for sharing.