title: Google Chromecast sender error if Chromecast extension is not installed or using incognito
body: <p>I'm having an error running Chromecast sender in Chrome Incognito or if Chromecast extension is not installed:</p>
  
  <pre><code>Failed to load resource: net::ERR_ADDRESS_UNREACHABLE chrome-extension://boadgeojelhgndaghljhdicfkmllpafd/cast_sender.js
  Failed to load resource: net::ERR_ADDRESS_UNREACHABLE chrome-extension://dliochdbjfkdbacpmhlcpmleaejidimm/cast_sender.js
  Failed to load resource: net::ERR_ADDRESS_UNREACHABLE chrome-extension://hfaagokkkhdbgiakmmlclaapfelnkoah/cast_sender.js
  Failed to load resource: net::ERR_ADDRESS_UNREACHABLE chrome-extension://fmfcbgogabcbclcofgocippekhfcmgfj/cast_sender.js
  Failed to load resource: net::ERR_ADDRESS_UNREACHABLE chrome-extension://enhhojjnijigcajfphajepfemndkmdlo/cast_sender.js
  No cast extension found
  </code></pre>
  
  <p>Google cast sender is trying to send AJAX requests for local "cast_sender.js". Should this happen or is there a better way to check if Chromecast sender extension exists (not by requesting AJAX request)?</p>
  
  <p>I believe these AJAX requests are a way of asking if Chromecast extension exists. Is there a better way to check if Chromecast extension exists?</p>