Hello,

THank you for this report!

Indeed, this is just the declaration for $translator not set where it should. (only the free version has this issue).

Don't worry, it's not a real bug, as no wrong behaviour.
The $translator variable is just to set the translation for the word "Translator" used in the list of flags, and for the tooltip when you hover a flag.

You just have to turn off the joomla error reporting in global configuration of Joomla.
This issue will be fixed in 3.5.2, but don't forget that on a online site, you should not turn on your error reporting to prevent security issue in frontend.

if you want to edit the file to remove the notice error, just copy/paste the line 493 :
$translator=JText::_('COM_ICAGENDA_TRANSLATOR');

At the top of the file, for example, on line 30

Hope this helps!
And thank you!

Regards,
Cyril