When trying to open an http(s) link in Dolphin, the webbrowser should be launched instead.
The codepath didn't take into account that it can be either a service or (when prefixed by an exclamation mark) an exec path. This had it try to exec the name of a desktop file which obviously didn't work.
The fallback to Konqueror is removed as its file viewer is just a Dolphin Part and it isn't installed by default these days anymore.