Theme changing does not work correctly

[masterjp]

It is the first time, I switched from Standard theme to fusion and fusion dark.

Standard and Fusion are very light surfaces and Fusion dark, as the same says, a very dark theme.
If I switch from Fusion dark to Fusion theme, the XnView MP windows are dark again.

After a restart of XnView MP, it looks correct. Maybe it is an error or is it normal?