How to change pre-2017 Splunkbase app icon background from white to transparent?

[helge]

We have several apps in Splunkbase that were first published before 2017. As explained in this answer, the default app icon background was changed from white to transparent in 2017. Since our apps are older, they still have the white background, which does not look so great with rounded corners:

How can we get the background changed from white to transparent?

Notes:

• In the icon's PNG the corners have always been transparent.
• We don't specify a color in default.xml

[helge · Accepted solution]

To change the Splunkbase icon background of an app that was first published before ca. 2017 do the following:

1. Create a new app version with color="transparent" in default.xml
2. Upload the new app package to Splunkbase; the icon background changes immediately
3. Delete the new app version from Splunkbase without ever having published it
4. Voilà: you have a transparent background without the need to release a new app version