Below test fails intermittently on Linux in the GitHub Actions test run.

2021-05-06T10:27:19.6546656Z test.javafx.css.HonorDeveloperSettingsTest > testOpacityWithManuallyChangedValueAndInlineStyleIsSetToInlineStyle FAILED
2021-05-06T10:27:19.6549284Z java.lang.NullPointerException
2021-05-06T10:27:19.6550829Z at javafx.graphics/javafx.scene.Node.notifyParentsOfInvalidatedCSS(Node.java:9295)
2021-05-06T10:27:19.6552527Z at javafx.graphics/javafx.scene.Node.reapplyCSS(Node.java:9342)
2021-05-06T10:27:19.6553757Z at javafx.graphics/javafx.scene.Node$1.reapplyCSS(Node.java:588)
2021-05-06T10:27:19.6555253Z at javafx.graphics/com.sun.javafx.scene.NodeHelper.reapplyCSS(NodeHelper.java:283)
2021-05-06T10:27:19.6557553Z at javafx.graphics/com.sun.javafx.css.StyleManager.userAgentStylesheetsChanged(StyleManager.java:1514)
2021-05-06T10:27:19.6560309Z at javafx.graphics/com.sun.javafx.css.StyleManager.setDefaultUserAgentStylesheet(StyleManager.java:1365)
2021-05-06T10:27:19.6563106Z at javafx.graphics/com.sun.javafx.css.StyleManager.setDefaultUserAgentStylesheet(StyleManager.java:1347)
2021-05-06T10:27:19.6571692Z at test.javafx.css.HonorDeveloperSettingsTest.setUp(HonorDeveloperSettingsTest.java:89)