Splash API/lua error: attempt to index local element (a nil value)

Question

I'm writing a lua script that I want to use with scrapy + splash for a website. I want to write a script that enters a text and then clicks on a button. I have the following code:

function main(splash)
   local url = splash.args.url
   assert(splash:go(url))
   assert(splash:wait(5))

   local element = splash:select('.input_29SQWm')
   assert(element:send_text("Wall Street, New York"))
   assert(splash:send_keys("<Return>"))
   assert(splash:wait(5))

   return {
     html = splash:html(),
   }
end

Right now I'm using the splash API to test if my code runs properly. When I click "Render!" I get the following message:

{
  "info": {
      "message": "Lua error: [string \"function main(splash)\r...\"]:7: attempt to index local 'element' (a nil value)",
      "type": "LUA_ERROR",
      "error": "attempt to index local 'element' (a nil value)",
      "source": "[string \"function main(splash)\r...\"]",
      "line_number": 7
  },
  "error": 400,
  "type": "ScriptError",
  "description": "Error happened while executing Lua script"
}

So for some reason element is still nil when I try to send "Wall street, New York". I don't understand why; if I enter the following in chrome console:

$('.input_29SQWm')

I find the desired element!

Q: Does anyone know what I'm doing wrong?

Thanks in advance!