Strict warning: Creating default object I am getting this error on my website. 


  Strict warning: Creating default object from empty value in theme541_preprocess_html()


I found a patch https://www.drupal.org/node/1242362 by Damien McKenna but I don't know how to apply the patch that fixes the error.
Applying patches is not actually a drupal specific issue and would be better on stack exchange, however there is a drupal documentation page so...

Check out the applying patches documentation.

However having said that, if you read that issue then you can see that patch was committed to that module 3 years ago and if you are using the latest release of the boron module (7.x-1.4) then that patch is already in there.

If you are applying the patch to something that isn't the boron theme then it will likely not work.