Quoting

nope

@@ -5,19 +5,19 @@ usage() {
 	echo opens files
 }
 
-case $@ in
+case "$@" in
 	--help)
 		usage
 		exit 1
 		;;
 	*.pdf)
-		okular $@ > /dev/null 2>&1 &
+		okular "$@" > /dev/null 2>&1 &
 		;;
 	*.html)
-		firefox $@ > /dev/null 2>&1 &
+		firefox "$@" > /dev/null 2>&1 &
 		;;
 	*.mp4|*.mp3)
-		vlc $@ > /dev/null 2>&1 &
+		vlc "$@" > /dev/null 2>&1 &
 		;;
 	*)
 		echo "No rule for opening this file has been specified"