Themes get mixed up when switching file

Describe the bug
The colouring of title-bar and background are not consistent.
Opening the preview on a folder, exe, text-document, html, ... there is a white title bar
Opening the preview on a png or jpg the title bar is black.

Now that's all good and I have no problem with that but here comes the bug:
Starting the preview on one filetype and switching to another leaves a grey titlebar with black or white font.

Original/Intended look	Bug

So the font-colour is chosen correctly to match the underlying filetype but the background of the titlebar and the background of the preview don't fit

To Reproduce
Steps to reproduce the behavior:

1. Start preview on a file
2. Change underlying file to a different filetype (of different color-scheme) without closing the preview
3. Preview now has a different colouring as it has when opening directly on that second file

Desktop (please complete the following information):

• OS Version: Win 7
• QuickLook Version: 3.6.5 msi

Is this related to Windows 7 or does it also happen on Windows 10?

Start by reproducing the issue using the listed steps: open a preview, switch to a different file type without closing it, and compare the result with opening that file directly. Trace the preview's theme and title-bar updates during file switching, then verify that the title bar and preview background match the selected file type on Windows 7 and, if available, Windows 10.