Fix corrupted HEALTH_URL and ASCII art in Dockerfiles caused by version updater

The addons_updater script's global sed replacement corrupted Dockerfiles
when the upstream_version was empty (""), replacing all empty double-quoted
strings with version strings. This corrupted:

- HEALTH_URL values (causing malformed health check URLs and container
  instability from failed health checks)
- ASCII art comments in Dockerfile headers

Fixed affected addons: guacamole, tdarr, photoprism, enedisgateway2mqtt_dev,
gazpar2mqtt, seafile

Also added a guard in the updater script to skip updates when version
strings are empty, preventing this corruption from recurring.

Co-authored-by: alexbelgium <44178713+alexbelgium@users.noreply.github.com>

enedisgateway2mqtt_dev/Dockerfile

@@ -2,11 +2,11 @@
 #  ALEXBELGIUM'S DOCKERFILE  #
 #============================#
 #           _.------.
-#       _.-`    ('>.-`"0.8.13""-.
+#       _.-`    ('>.-`"""-.
 # '.--'`       _'`   _ .--.)
 #    -'         '-.-';`   `
 #    ' -      _.'  ``'--.
-#        '---`    .-'"0.8.13"`
+#        '---`    .-'""`
 #               /`
 #=== Home Assistant Addon ===#