Emacs returns either a sequence of availbale displays or nil. Checking nil fixes this script to work as expected.
@@ -3,7 +3,7 @@
# get list of available X windows.
x=`emacsclient --alternate-editor '' --eval '(x-display-list)' 2>/dev/null`
-if [ -z "$x" ] ;then
+if [ -z "$x" ] || [ "$x" = "nil" ] ;then
# Create one if there is no X window yet.
emacsclient --alternate-editor "" --create-frame "$@"
else