bash-completion: Fix device completion for pacat

The Bash shell completion for pacat --device combines the name of the
last sink and the name of the first source. This patch fixes that by
adding a whitespace separator in the list of devices.

Buglink: https://bugs.freedesktop.org/show_bug.cgi?id=68106

shell-completion/pulseaudio-bash-completion.sh

@@ -452,7 +452,7 @@ _pacat () {
         --device=*)
             cur=${cur#*=}
             comps=$(__sinks)
-            comps+=$(__sources)
+            comps+=" "$(__sources)
             COMPREPLY=($(compgen -W '${comps[*]}' -- "$cur"))
             ;;
 
@@ -481,7 +481,7 @@ _pacat () {
         -s) _known_hosts_real "$cur" ;;
         -d)
             comps=$(__sinks)
-            comps+=$(__sources)
+            comps+=" "$(__sources)
             COMPREPLY=($(compgen -W '${comps[*]}' -- "$cur"))
             ;;
     esac