NullPointerException during generating Heap-File

[Necoro]

On first launch of Isabelle/Eclipse, it wanted to (re)build the HOL-Image. While doing so, I switched desktops and on coming back, Eclipse was frozen and I got the following traceback on the console:

Done launching
Exception in thread "session_actor" java.lang.NullPointerException
at isabelle.Isabelle_Process.input_bytes(isabelle_process.scala:392)
at isabelle.Isabelle_Process.input(isabelle_process.scala:397)
at isabelle.Protocol$class.discontinue_execution(protocol.scala:273)
at isabelle.Session$$anonfun$3$$anonfun$apply$mcV$sp$3$$anon$2.discontinue_execution(session.scala:394)
at isabelle.Session$$anonfun$3$$anonfun$apply$mcV$sp$3.applyOrElse(session.scala:416)
at scala.runtime.AbstractPartialFunction$mcVL$sp.apply$mcVL$sp(AbstractPartialFunction.scala:33)
at scala.runtime.AbstractPartialFunction$mcVL$sp.apply(AbstractPartialFunction.scala:33)
at scala.runtime.AbstractPartialFunction$mcVL$sp.apply(AbstractPartialFunction.scala:25)
at scala.actors.InternalActor$class.receiveWithin(InternalActor.scala:206)
at scala.actors.ActorProxy.receiveWithin(ActorProxy.scala:19)
at scala.actors.Actor$.receiveWithin(Actor.scala:199)
at isabelle.Session$$anonfun$3.apply$mcV$sp(session.scala:388)
at isabelle.Simple_Thread$$anonfun$2.apply$mcV$sp(simple_thread.scala:52)
at isabelle.Simple_Thread$$anon$2.run(simple_thread.scala:30)