Warning: Trying to access array offset on value of type null in /mnt/web111/d2/02/58098402/htdocs/logopaedie-legden/mail_code.php on line 183

Fatal error: Uncaught TypeError: filtereKyrillischeZeichen(): Argument #1 ($eingabe) must be of type string, null given, called in /mnt/web111/d2/02/58098402/htdocs/logopaedie-legden/mail_code.php on line 183 and defined in /mnt/web111/d2/02/58098402/htdocs/logopaedie-legden/mail_code.php:174
Stack trace:
#0 /mnt/web111/d2/02/58098402/htdocs/logopaedie-legden/mail_code.php(183): filtereKyrillischeZeichen()
#1 /mnt/web111/d2/02/58098402/htdocs/logopaedie-legden/index.php(23): include('...')
#2 {main}
  thrown in /mnt/web111/d2/02/58098402/htdocs/logopaedie-legden/mail_code.php on line 174