Can you please remove all your current files and re-download, (you can also try the version from git, or wait till Monday when 5.5.1 may be released)
I did just as you say. The same error.
I had add empty function view() into /concrete/libraries/controller.php and message is gone, but imho its wrong way.
I had add empty function view() into /concrete/libraries/controller.php and message is gone, but imho its wrong way.
After installation concrete5.5.0 i get this message :
All steps was default.