Fix preview layout crash upon screen rotation

Preview layouts are rendered via LauncherAppWidgetHostView. These
layouts are not yet added to the launcher. And thus, there is no
LauncherAppWidgetInfo.

Test: When a preview layout is shown in the recommended widget section,
      rotate the screen. No crash is observed.
Bug: 190395009
Change-Id: Ib1d080a106681fbfe3a4293f9f51f9576ef9414b