this line of code is used to retrieve your Netatmo modules, connected to your weather station.
What are you seeing, are not errors, but PHP notifies. You have maybe turn on "Error reporting" to "verbose".
Please, go in Joomla global configuration panel and set "Error reporting" to "Default".
If this solution does not let your notifies disappear, please, open a ticket under Tech Support:
and send us a valid Super Admin account to login in the backend of your website, and we will fix it.