When the language translation strings are not present for a plugin, the entire page does not show any language keys.
For example: I have a plugin called Backup.
The default language of the site is say, Russian. My plugin does not have language keys for Russion. When the page is installed, no text appears..
When the equivalent language string is not present, default language should be shown.
Even worse is that if "setErrorMessage" function is used for an Validator class, the page throws 505 Internal error.