New Image Dialog - Can only add a single number at a time in the Width or Height fields

Preconditions: Enable the Image Dialog from the WYSIWYG Editor section in the Wiki Administration: look for 'xwiki-image' in the drop down of disabled CKEditor plugins and uncheck it then save.

Steps to reproduce:

1. Edit a page and add some text
2. Click on the Image icon and upload any image then Select
3. Click on the Advanced tab and click in the Width or Height field
4. Add a number eg. 400

Expected results: The user can add what number he desires.

Actual results: Once the user adds the first number, in this case 4, the field is not active anymore - the mouse courser is removed from that field and the user has to click again to add one more number and again for another.