Fix warnings in latest version of Crystal

src/invidious/helpers/i18n.cr

@@ -24,6 +24,8 @@ def translate(locale : Hash(String, JSON::Any) | Nil, translation : String, text
       if !locale[translation].as_s.empty?
         translation = locale[translation].as_s
       end
+    else
+      raise "Invalid translation #{translation}"
     end
   end