QImageReader does not support jpg when first called without an active QCoreApplication

It seems that when the first call to QImageReader is done without an active QCoreApplication it seems to not get the feature to import jpg-formats.

It is not even needed to import an image, I could resolve my issue by just adding this to my code:

{
  QCoreApplication app;
  QImageReader;
}

Once initialized like this the QCoreApplication does not seem to be required anymore.
Also I could reproduce this just with a release-build, it worked with a debug-build.