Ruby TypeError: no implicit conversion of String into Integer

I am trying to find if there is mango/cc: in my data and if its there update its value to new_version, if its not there add mango/cc:#{new_version}

My data

{"product"=>"fruit", "id"=>"alpha", "details"=>{"SS"=>["mango/aa:50", "mango/cc:287_457_51.0.0"]}}

Code:

  new_version = "287_457_53.0.0"
  var1 = data['details']['SS'].select{|x| x.start_with?('mango/cc:')}
  if var1.empty?
    data['details'] << "mango/cc:#{new_version}"
  else
    data['details'].delete(var1)
    data['details'] << "mango/cc:#{new_version}"
    puts data

Current Output:

`[]': no implicit conversion of String into Integer (TypeError)

Expected Output:

{"product"=>"fruit", "id"=>"alpha", "details"=>{"SS"=>["mango/aa:50", "mango/cc:287_457_53.0.0"]}}