Polygon-smooth crashes when dealing with MultiPolygons including more than one polygon with hole(s)

[Pitouli]

For example, if you test on this MultiPolygon, it will crashes:

{
  "type": "MultiPolygon",
  "coordinates": [
    [
      [
        [102.0, 2.0],
        [103.0, 2.0],
        [103.0, 3.0],
        [102.0, 3.0],
        [102.0, 2.0]
      ]
    ],
    [
      [
        [100.0, 0.0],
        [101.0, 0.0],
        [101.0, 1.0],
        [100.0, 1.0],
        [100.0, 0.0]
      ],
      [
        [100.2, 0.2],
        [100.8, 0.2],
        [100.8, 0.8],
        [100.2, 0.8],
        [100.2, 0.2]
      ]
    ],
    [
      [
        [105.0, 0.0],
        [106.0, 0.0],
        [106.0, 1.0],
        [105.0, 1.0],
        [105.0, 0.0]
      ],
      [
        [105.2, 0.2],
        [105.8, 0.2],
        [105.8, 0.8],
        [105.2, 0.8],
        [105.2, 0.2]
      ]
    ]
  ]
}

I found the issue and I am sending a PR (I simply create this ticket to link the PR to it)

[rowanwins]

Resolved by #2324