XMLHttpRequest read file only work in debug with QT Creator

[ichi]

Sorry if this question has an obvious answer.
I am a noob in QT/QML
I made a very simple app who can read a local text file from the XMLHttpRequest example on stack.
It works flawlessly.
I have set the parameter
QML_XHR_ALLOW_FILE_READ=1

Nothing in the debug window, the behavior of the app is perfect.
It is a simple Main.qml file.
The text in my file is shown in the window as it should.

BUT, when I choose the release option from the build type, and close the QT Creator App, the app cannot read files anymore. As soon as I close QT Creator the app seems to be unable to perform XMLHttpRequest.

Am I missing something to make this possible? I can't find it.

Thanks in advance for the attention you put in reading this message. I'm learning C++ to handle the files, but I wish this could work...