Addon structures will save with null data and brick the vehicle

[SprocketTools]

Describe the bug Addon structures will often times save without any data, like this:

{
      "vuid": 4,
      "type": "plateStructureMesh",
      "meshData": {
        "v": "0.1",
        "smoothAngle": 0,
        "gridSize": 1,
        "format": "freeform",
        "mesh": {
          "majorVersion": 0,
          "minorVersion": 3,
          "vertices": [],
          "edges": [],
          "edgeFlags": [],
          "faces": []
        },
        "rivets": {
          "profiles": [
            {
              "model": 0,
              "spacing": 0.1,
              "diameter": 0.05,
              "height": 0.025,
              "padding": 0.04
            }
          ],
          "nodes": []
        }
      }
    },

Version 0.2.19.1

To Reproduce The easiest way to reproduce this bug is to create a new design, place a standard addon structure down, then save. The blueprint will have a null structure, while reloading the file deletes the structure. I've also observed these in other vehicles that are unable to load.

[SprocketTools]

Actually, it appears that duplicates were saved here

[SprocketTools]

Similar behavior has also been found with addon structure "blueprints" and "objects" - phantom items will get saved into the blueprint despite not existing in the tank.

[Muushy]

Fixed in 0.2.19.3