agent plugins: "Open Containing Folder" action shows error page

[jruales]

Testing #297147

When I click to "Open Containing Folder", I see an error page "The file is not displayed in the text editor because it is a directory". It's true that it works to click "Open Folder" in the error page, but the fact that there's an error page to begin with makes it a bad experience.

error-open-containing-folder.mov

[jruales]

Verified now it opens the Finder on that folder