FULL PRODUCT VERSION :
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Mac OS version: 10.12.6 (16G29)

A DESCRIPTION OF THE PROBLEM :
When using a FileChooser-Dialog and setting the parent stage to be not resizable
    stage.setResizable(false);
the user will be able to enter the Fullscreenmode after cancelling the FileChooser-Dialog.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
 - setResizable(false) on stage
 - open FileChooser anywhere
 - press "Cancel" on FileChooser

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The stage is the same as before
ACTUAL -
The green Fullscreen-Btn will be enabled

REPRODUCIBILITY :
This bug can be reproduced always.