update np-subsonic script

it seems to return "" when it doesn't have any data (network down)

.config/zsh/functions/np-subsonic

@@ -23,7 +23,8 @@ local entry=$(jq '."subsonic-response".nowPlaying.entry[0]' <<<${response})
 local title=$(jq --raw-output .title <<< ${entry})
 local artist=$(jq --raw-output .artist <<< ${entry})
 
-if [[ "${title}" != "null" && "${artist}" != "null" ]]; then
+if [[ "${title}" != "" && "${artist}" != "" ]] \
+    && [[ "${title}" != "null" && "${artist}" != "null" ]]; then
     print ${title} – ${artist}
 else
     return 1