Not empty modal when Version Mandatory Summary is enabled

Steps to reproduce:

• login
• go to Admin Section -> Edit Mode Settings -> Enable version summary . Set this to YES
• go to a page or create a page, and don't fill the Version Summary field.
• click Save and View

You will get a modal which forces you to write a summary. On IE8 and IE9, the modal windows already has the value of "undefined"

2 remarks:

• this is inconsistent with Firefox Browsers, which have this field blank by default. And IMO this is the correct behavior
• we could use a xwiki type of modal, not a js one, but this is another issue.