PyroCMS中的错误：非静态方法Lex_Parser :: inject_noparse（）不应该静态调用

I have inherited a CMS system called PyroCMS and it is showing an error. I am not familiar with this CMS so any suggestions would be welcome.

"A PHP Error was encountered Severity: 8192 Message: Non-static method Lex_Parser::inject_noparse() should not be called statically, assuming $this from incompatible context Filename: libraries/Template.php Line Number: 285"

Here is the relevant piece of code from the Template file.

// Now that *all* parsing is sure to be done we inject the {{ noparse }} contents back into the output
if (class_exists('Lex_Parser')) {
    $this->_body = Lex_Parser::inject_noparse($this->_body);
}

// Want it returned or output to browser?
if (!$return) {
    $this->_ci->output->set_output($this->_body);
}

return $this->_body;
}

I have searched extensively for any clue as to what might be causing this but all I can come up with is dozens of other sites with the same issue

Thank you for taking the time to help.