update_plugins.php fails if plugin is missing

[saadbruno]

code/bin/update_plugins.php is the script we run when updating plugins via cron.

When an existing plugin listed in our database gets deleted from GitHub, this script stops excecution:

updating plugin for Topodic/openrct2-scenery-scatterer-plugin
{"status":"error","message":"Error when adding plugin "}make: Leaving directory '/home/saad/dev/openrct2_plugin_repository/docker'

Wether we should delete the plugin from our database when it's missing from github or not is another question. But this script should keep updating the rest of the plugins regardless.