Solver is not fully immune to erroneous input

[rodyo]

As noted by Vasco Grilo:

The solver is not blinded against erroneous input. The following situations were detected :

• For equal initial and final positions, initial or final position at the central body, null gravitational parameter, or null time of flight, the initial and final velocity components are NaN .
• For negative gravitational parameter, the initial and final velocity components have an imaginary part .
• For negative time of flight, the initial and final velocity components are real.

For all these cases, the exit flag is 1; which is supposed to indicate success, instead of -1; which indicates that the given problem has no solution. Therefore the outputted results could be interpreted as correct, and undermine the following calculations.