notification-spacex: fix when there are no upcoming launches (#451)

Author: krzys-h

polybar-scripts/notification-spacex/notification-spacex.sh

@@ -4,10 +4,10 @@ spacex_launch=$(curl -sf "https://ll.thespacedevs.com/2.2.0/launch/upcoming/?lsp
 
 if [ -n "$spacex_launch" ]; then
     spacex_precision=$(printf "%s" "$spacex_launch" | jq -r '.results[0].net_precision.abbrev' )
-    spacex_timestamp=$(date +"%s" --date "$(printf "%s" "$spacex_launch" | jq -r '.results[0].net' )")
-    spacex_duration=$((spacex_timestamp - $(date +%s)))
 
     if [ "$spacex_precision" = "HR" ] || [ "$spacex_precision" = "MIN" ] || [ "$spacex_precision" = "SEC" ]; then
+        spacex_timestamp=$(date +"%s" --date "$(printf "%s" "$spacex_launch" | jq -r '.results[0].net' )")
+        spacex_duration=$((spacex_timestamp - $(date +%s)))
         if [ "$spacex_duration" -lt 43200 ] && [ "$spacex_duration" -gt 0 ]; then
             echo "# $(date +"%H:%M" -u --date @$spacex_duration)"
         else