Redirect dcop/qdbus stderr to /dev/null.

Even if we have e.g. dcop installed we may not have dcopserver running
and providing completions.

contrib/qdbus

@@ -8,8 +8,8 @@ _qdbus()
     COMPREPLY=()
     cur=`_get_cword`
     [ -n "$cur" ] && unset COMP_WORDS[${#COMP_WORDS[@]}-1]
-    COMPREPLY=( $( compgen -W '$( command ${COMP_WORDS[@]} | sed s/\(.*\)// )' \
-        -- "$cur" ) )
+    COMPREPLY=( $( compgen -W '$( command ${COMP_WORDS[@]} 2>/dev/null | \
+        sed s/\(.*\)// )' -- "$cur" ) )
 } &&
 complete -F _qdbus qdbus dcop