[THREESCALE-11435] Check for nil value when decode based64 value

[tkan145]

What

Fix THREESCALE-11435

Verification steps:

• Checkout this branch
• Create apicast-config.json with the following

cat <<EOF >apicast-config.json
{
  "services": [
    {
      "backend_version": "2",
      "id": "1",
      "proxy": {
        "credentials_location": "authorization",
        "hosts": [
          "one"
        ],
        "api_backend": "https://echo-api.3scale.net:443",
        "backend": {
          "endpoint": "http://localhost:8081",
          "host": "backend"                   
        },
        "policy_chain": [
          {
            "name": "routing",
            "version": "builtin",
            "enabled": true,
            "configuration": {
              "rules": [
                {
                  "url": "https://echo-api.3scale.net:443",
                  "owner_id": 119084,
                  "owner_type": "BackendApi",
                  "condition": {
                      "operations": [
                          {
                              "match": "path",
                              "op": "matches",
                              "value": "^(/test/.*|/test/?)"
                          }
                      ]
                  },
                  "replace_path": "{{uri | remove_first: '/test'}}"
                }
              ]
            }
          },
          {
            "name": "apicast.policy.apicast"
          }
        ],
        "proxy_rules": [
          {
            "http_method": "GET",
            "pattern": "/test",
            "metric_system_name": "hits",
            "delta": 1,
            "parameters": [],
            "querystring_parameters": {}
          }
        ]
      }
    }
  ]
}
EOF

• Start development env

make development

• Start APIcast

THREESCALE_DEPLOYMENT_ENV=staging APICAST_LOG_LEVEL=debug APICAST_WORKER=1 APICAST_CONFIGURATION_LOADER=lazy APICAST_CONFIGURATION_CACHE=0  THREESCALE_CONFIG_FILE=apicast-config.json  ./bin/apicast

• Capture APIcast IP

APICAST_IP=$(docker inspect apicast_build_0-development-1 | yq e -P '.[0].NetworkSettings.Networks.apicast_build_0_default.IPAddress' -)

• Send request

curl -i -k -H "Host: one" -H "Accept: application/json" "http://${APICAST_IP}:8080/?user_key="

• You should get 401 response back

HTTP/1.1 401 Unauthorized              
Server: openresty                      
Date: Wed, 06 Nov 2024 03:25:13 GMT    
Content-Type: text/plain; charset=utf-8
Transfer-Encoding: chunked             
Connection: keep-alive                 
                                       
Authentication parameters missing%