No "Continue" button when installing a flavor with a specific version in the distribution wizard

Steps to reproduce :

• On a clean XWiki farm, log-in as administrator
• Go in the wiki manager and click on "Create sub-wiki"
• Select the option "No flavor, let the wiki be empty" in the flavor selection
• Click on next, and next again to trigger the wiki creation
• Once the wiki creation is finished, click on the button "Go to the wiki", you'll access a distribution wizard (as the wiki has no flavor installed yet)
• Select the XWiki Standard flavor in the flavor list, click on "Install this flavor"
• In the next screen, don't click yet on "Install", click on "Show details" and then on "Standard Versions" to list all the flavor versions
• Select a version that you want to install, you can even choose the same version as your current XWiki version, it will trigger the bug
• Once the version is selected, you'll have a page similar to this one :
  
• Note that here, we don't have any "Skip" button on the botton-right corner of the screen
• From that, you can install the flavor, you won't get any "Continue" button at all
• You need to restart the server to continue to the wiki

Marking as Critical as this disturbs the user flow and forces the user to restart the server.