fix: Do no render empty declarations

[ddecrulle]

We do not want to render declaration component when there is not label.

Today, this declaration will render a div without text :

{
  "declarations": [
    {
      "label": {
        "type": "VTL|MD",
        "value": '""',
      },
      "position": "BEFORE_QUESTION_TEXT",
    },
  ]
}

This PR resolve this issue https://github.com/InseeFr/Lunatic-DSFR/issues/174

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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