Fix padding in the "insert table" dialog in TinyMCE

VERSIONS: Grappelli 2.5.1, Django 1.6.1
STATICFILES: OK.
JAVASCRIPTS: OK
CUSTOMIZATIONS: NONE

If you enable the "table" plugin in TinyMCE and try to insert a table, the table dialog has no margin on the top. That's because the "body > *:first-child { margin-top: 20px }" CSS rule gets applied to an invisible element.