FEATURE: Check if selectable avatars exist before enabling them (#10032)

lib/validators/selectable_avatars_enabled_validator.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class SelectableAvatarsEnabledValidator
+  def initialize(opts = {})
+    @opts = opts
+  end
+
+  def valid_value?(value)
+    value == "f" || SiteSetting.selectable_avatars.split("\n").size > 1
+  end
+
+  def error_message
+    I18n.t('site_settings.errors.empty_selectable_avatars')
+  end
+end