Empty securities in operation are not included in converted spec

[HugoMario]

When converting from 2.0 to 3.0.0

"swagger": "2.0",
...
"securityDefinitions": {
    "api_key": {
      "type": "apiKey",
      "name": "api_key",
      "in": "header"
    },
    "api_key2": {
      "type": "apiKey",
      "name": "api_key2",
      "in": "query"
    },
    "petstore_auth": {
      "type": "oauth2",
      "authorizationUrl": "http://petstore.swagger.io/api/oauth/dialog",
      "flow": "implicit",
      "scopes": {
        "write:pets": "modify pets in your account",
        "read:pets": "read your pets"
      }
    }
  },
"security": [
    {
      "api_key": [],
      "petstore_auth": [
        "write:pets",
        "read:pets"
      ]
    }
  ],
...
"/user/logout": {
      "get": {
        "tags": [
          "user"
        ],
        "summary": "Logs out current logged in user session",
        "description": "",
        "operationId": "logoutUser",
        "produces": [
          "application/json",
          "application/xml"
        ],
        "responses": {
          "default": {
            "description": "successful operation"
          }
        },
        "security": []
      }
    },

"openapi": "3.0.0",
...
"/user/logout": {
      "get": {
        "tags": [
          "user"
        ],
        "summary": "Logs out current logged in user session",
        "operationId": "logoutUser",
        "responses": {
          "default": {
            "description": "successful operation"
          }
        }
      }
    },