WebEngineView: Using offTheRecord profile with Pepper Flash plugin leads to assert in debug mode

When using the Pepper Flash Plugin and loading a page with flash content into WebEngineView, which has offTheRecord profile set, there is the following assert in debug mode:
[0114/222123:FATAL:pepper_flash_file_message_filter.cc(56)] Check failed:
false.
The problem raises from Chromium, which hits NOTREACHED() when it gets empty user profile data directory path - even in offTheRecord/incognito mode.
This could be fixed by returning a non-empty path also in incognito mode, but is that really a right way to do it.