Check if the internal_tls_config is not null when get strong_ssl_ciph…

[stonezdj]

…er value

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[MinerYang]

lgtm

[zyyw]

Do we need to add # strong_ssl_ciphers: false here:

https:
  # https port for harbor, default is 443
  port: 443
  # The path of cert and key files for nginx
  certificate: /your/certificate/path
  private_key: /your/private/key/path
  # enable strong ssl ciphers (default: false)
  # strong_ssl_ciphers: false