Calling solve while no vehicle has been defined (e.g. by commenting out this line in the libvroom example result in a segfault with a release build. This is likely the reason for VROOM-Project/pyvroom#118.

With a debug build, we hit an assertion when solving without any vehicle (or job) defined. We do have checks throwing exceptions while parsing json instances, but we should move those up to Input so that the same filters out json parsing and C++ calls.