I think that'll break if the "Named Clipboard Switcher" is open but minimised. This script should cater for that eventuality as well:
tell application "System Events"
tell application process "Keyboard Maestro Engine"
try
set value of attribute "AXMinimized" of item 1 of (every window whose name is "Clipboard History Switcher") to false
return 1
on error
try
set value of attribute "AXMinimized" of item 1 of (every window whose name is "Named Clipboard Switcher") to false
on error
-- do nothing
end try
return 0
end try
end tell
end tell
You could do away with the error blocks and use your "get list, if list count > 0" construct if you prefer that more explicit way of doing things.