Import fails if the user enters this URL /xwiki/bin/admin/XWiki/XWikiPreferences manually

The form in import.vm says

<form action="">

When the administration application is absent, the action is "admin" so when you try to import you are sent to the bad action.

It displays the message:

Importing xwiki-application-administration-1.2.xar: Error while preparing importing

• 0 Document(s) installed
• 0 Document(s) skipped
• 0 Document(s) with error

As if the import failed when it fact it was not even started.

The form needs to call the import action

<form action="$doc.getURL("import")">