Steps to reproduce the issue:
1. Go to blogs -> Add entry (either from Site Admin or adding the portlet to a page)
2. When adding the blog entry drag and drop a image to the cover image.
3. Don't type anything in the title.
4. Fill the content with some data.
5. Click publish.
At this point the blog entry won't be added because the title is a mandatory field, so the screen will display an error saying that you need to add a title. However, the cover image has disappeared and it shouldn't, it should still keep the cover image.
Same happens with the Abstract Image in the Settings section.