sbt reported "Exception in thread "AWT-EventQueue-0" java.util.ConcurrentModificationException: mutation occurred during iteration" with sample plot codes

[liang3zy22]

Steps:

1. Use following build.sbt file:

   ThisBuild / scalaVersion := "2.13.7"

   libraryDependencies += "org.scalanlp" %% "breeze" % "2.0.1-RC2"

   libraryDependencies += "org.scalanlp" %% "breeze-viz" % "2.0.1-RC2"

2. The main scala codes:
   implicit val randss = RandBasis.mt0
val f = Figure()
val p = f.subplot(0)
val x = linspace(0.0,1.0)
p += plot(x, x ^:^ 2.0)
p += plot(x, x ^:^ 3.0, '.')
p.xlabel = "x axis"
p.ylabel = "y axis"
f.saveas("lines.png")
val p2 = f.subplot(2,1,1)
val g = Gaussian(0,1)
p2 += hist(g.sample(100000),100)
p2.title = "A normal distribution"
f.saveas("subplots.png")

3. Compile and run the codes.

Problem:
The sbt reported following error:
Exception in thread "AWT-EventQueue-0" java.util.ConcurrentModificationException: mutation occurred during iteration
at scala.collection.mutable.MutationTracker$.checkMutations(MutationTracker.scala:43)
at scala.collection.mutable.CheckedIndexedSeqView$CheckedIterator.hasNext(CheckedIndexedSeqView.scala:47)
at scala.collection.IterableOnceOps.foreach(IterableOnce.scala:563)
at scala.collection.IterableOnceOps.foreach$(IterableOnce.scala:561)
at scala.collection.AbstractIterable.foreach(Iterable.scala:926)
at breeze.plot.Figure$$anon$1.run(Figure.scala:120)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Expected:
No error

NOTES:
From the codes, the following part may cause the issue:
for (plot <- plots) {
contents.add(plot match { case Some(plot) => plot.panel; case None => new JPanel() })
}