``` java.lang.NullPointerException: Can not set a ...

# tornadofx

[seiv]

java.lang.NullPointerException: Can not set a null value for an Attribute
	at org.jdom.Attribute.setValue(Attribute.java:482)
	at org.jdom.Attribute.<init>(Attribute.java:221)
	at org.jdom.Attribute.<init>(Attribute.java:244)
	at org.jdom.Element.setAttribute(Element.java:1302)
	at no.tornado.tornadofx.idea.configurations.TornadoFXConfiguration.writeExternal(TornadoFXConfiguration.kt:116)
...

[SiebelsTim]

https://github.com/edvin/tornadofx-idea-plugin/pull/84