AppleScript and Finder - How to detect an "empty" selection when copying paths to the clipboard (Expanded Question)

I'm trying to build a Service that does the following:

• If some folder/files are selected in Finder, copy (all) the paths to the clipboard
• If nothing is selected, copy the "Path" of the window.

Digging around and getting inspiration from posts such as Copying the current directory's path to the clipboard and MacYourself's Copy file or folder path to the clipboard in Mac OS X Lion I've got to the point where I can get the paths of the selection, but I seem to be stuck when trying to get the path of the current window if selection empty.

UPDATE 13-Dec-2013. I've got some useful feedback (see https://apple.stackexchange.com/a/113612/7488; thanks @Flavin) so I have updated the code to the one below:

    on run {input, parameters}

        set l to {}
        tell application "Finder"
            set sel to (get selection)
            if not sel = {} then -- there are some file/folders selected

                repeat with f in (get selection)
                    set end of l to POSIX path of (f as alias)
                end repeat

            else --no stuff is selected, get the current location path

                set end of l to POSIX path of (insertion location as alias)

            end if
        end tell
        set text item delimiters to linefeed
        set the clipboard to (l as text)

    end run

The logic seems solid, and it works as long as I have "something" selected in Finder.

I suspect that the Service might not be "Active" when there is nothing selected, (that is, when the desired result would be to copy the current path to the clipboard).

In this situation, the Finder window appears thusly:

But trying to active the Service shows an "empty" service list:

When I have something selected, the Services list is populated:

The "Copy File Path" that I've defined is associated with "Files and Folders" in the Services Preferences -- what might be the issue?

I think = is what you're looking for.

set sel to (get selection)
if not sel = {} then
    --stuff is selected
else
    --no stuff is selected
end if

Or remove the not and flip the cases

set sel to (get selection)
if sel = {} then
    --no stuff is selected
else
    --stuff is selected
end if

It now works. The key is on how the "Automator" service is defined.

When initially configured, the Automator Service was defined as "Files or Folder" in "Finder":

So in the Preferences the Service is associated with Files and Folders:

And the result is that the service is not "active" when there is no selection (we get the same image than in the question):

Changing the definition of the service to "No Input":

Means that the Service is available when there is no selection in Finder:

Checking in the Services Preferences, now the Service is associated with the "General" category:

And the behavior is as expected.