When a custom control contains an HTMLEditor, Scene Builder can't load the control. The JAR Analysis Report indicates that calls to setHtmlText(...) or getHtmlText(...) are causing a NullPointerException. This happens regardless of whether or not the call is made from FXML or the controller's initialize block.

Using the same control outside of Scene Builder works as expected. I have posted a sample project here.

https://bitbucket.org/ryanjaeb/broken-fxml-control

Steps to reproduce:

1. Check out the above project.
2. Run "gradlew jar"
3. Attempt to import the JAR file from build/libs into Scene Builder.
4. The JAR Analysis Report will indicate an exception loading the control.

...
...
Caused by: java.lang.NullPointerException
at javafx.scene.web.HTMLEditor.setHtmlText(HTMLEditor.java:86)
at custom.CustomPaneController.initialize(CustomPaneController.java:11)
... 32 more