NPE at com.sun.javafx.css.StyleManager.findMatchingStyles(StyleManager.java:1308)

Application code is calling impl_processCSS().
At startup I get the NPE below: is there something changed in 8.0 compared to 2.2.6 that could explain it ?

java.lang.NullPointerException
    at com.sun.javafx.css.StyleManager.findMatchingStyles(StyleManager.java:1308)
    at com.sun.javafx.css.StyleHelper.setStyles(StyleHelper.java:172)
    at javafx.scene.Node.impl_processCSS(Node.java:7720)
    at javafx.scene.Parent.impl_processCSS(Parent.java:1168)
    at javafx.scene.Parent.impl_processCSS(Parent.java:1176)
    at javafx.scene.Parent.impl_processCSS(Parent.java:1176)
    at javafx.scene.Parent.impl_processCSS(Parent.java:1176)
    at javafx.scene.Parent.impl_processCSS(Parent.java:1176)
    at javafx.scene.Parent.impl_processCSS(Parent.java:1176)
    at javafx.scene.control.Control.impl_processCSS(Control.java:761)
    at javafx.scene.Parent.impl_processCSS(Parent.java:1176)
    at javafx.scene.Node.processCSS(Node.java:7657)
    at javafx.scene.Node.processCSS(Node.java:7651)
    at javafx.scene.Node.processCSS(Node.java:7651)
    at javafx.scene.Node.processCSS(Node.java:7651)
    at javafx.scene.Node.processCSS(Node.java:7651)
    at javafx.scene.Node.processCSS(Node.java:7651)
    at javafx.scene.Node.processCSS(Node.java:7651)
    at javafx.scene.Node.processCSS(Node.java:7651)
    at javafx.scene.Scene.doCSSPass(Scene.java:451)
    at javafx.scene.Scene.access$3800(Scene.java:176)
    at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2231)
    at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:349)
    at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:521)
    at com.sun.javafx.tk.quantum.QuantumToolkit$11.run(QuantumToolkit.java:374)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.access$200(Unknown Source)
    at com.sun.glass.ui.win.WinApplication$3$1.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:722)