My intent when parsing json what to ensure all vehicles either have no capacity key, or have all the same length for the capacity array. In particular I expect a missing capacity array to trigger an error. This happens for example when using:

{
  "vehicles": [
    {
      "id":0,
      ...
    },
    {
      "id":1,
      "capacity": [1],
      ...
    ],
    ...

resulting in an error with the message "Inconsistent capacity length: 1 and 0."

So far so good, but I just found out that reversing the order of vehicles above changes the behavior: we no longer get an error, instead the capacity for vehicle with id 0 is considered as zero and we move on with solving.
In this situation the vehicle won't get a route assigned if all tasks have a non-zero demand, so this is not such a big problem if considering that no capacity key means zero capacity.

Yet I think we should change this because:

• it would be more consistent to enforce always explicitly providing a capacity array as initially intended;
• it is clearer to get an error in the first place than to have to debug why those vehicles do not get routes (the reason I stumbled upon this);
• getting either a "usual" solution or an error just by changing vehicle order in input is not really acceptable.