Essay grading page does not display HTML in questions and answers

Teachers can't see essay questions properly when grading (if there is HTML in the question text, for example, image or table).
There is an issue in the mod/lesson/essay.php(line 404,405): function format_string is used to prepare texts. This function removes all HTML code from the text.

Since students are able to use WYSIWYG editor for answering the essay questions, format_string function should be changed to format_text function for both question and answer (lines 404 and 405).