BACKPORT - IE8: Extra empty files, text fields and browse buttons at image upload - IE8

In IE8 when doing specific actions you will get empty files and extra text fields and browse buttons
Chrome does not have a text input field, Firefox immediately opens the filebrowser. So this is won't work in those browsers

Reproduction path:
Build and run archetype version 1.05.07, Hippo CMS version 7.7.5

• Go to the CMS in IE8
• Go to Images
• Add image to a folder
  --> Add image dialog pops up (ATTACHMENT 1)
• Select with the browse... button an image an open (ATTACHMENT 2)
• Set cursor on the text field, left to the browsebutton and enter several spaces
• Press TAB twice
  --> An empty item is added (ATTACHMENT 3)
• Set cursor on the text field
• Press TAB twice
• Press space
• Click under the text field
  --> Extra text field and browse button is added (ATTACHMENT 4)

--> This process can be repeated for more empty items, text fields and buttons (ATTACHMENT 5)