Blogpost "Content" is not displayed on Blog homepage when creating/editing blogposts with Firefox and Summary is empty

Steps and results using Firefox:

• create a new blog article
• fill in the field "Content" but nothing on the field "Summary", tick Publish and click Save => at this point you'll see on the Main page of the Blog only the name of the blogpost
• edit the blog article and on the "Summary" field click Backspace a few times to delete all whitespace that may exist => at this point the "Content" is well displayed for the article on the Main page of the Blog
• edit again the article and click Save without any click or any modification => again the "Content" won't be displayed

Notes:

• I tested a clean XWiki instance with Firefox, Chrome 60 and IE11
• XWiki version: 9.7 on which I installed the Blog Application 9.5
• tested the above steps, it reproduces on FIREFOX 55, but not on Chrome and IE11