diff -r 64aad1e46f98 -r 97ccf48c2f0c src/Tools/Graphview/model.scala
--- a/src/Tools/Graphview/model.scala	Fri Mar 27 13:04:15 2020 +0100
+++ b/src/Tools/Graphview/model.scala	Fri Mar 27 22:01:27 2020 +0100
@@ -18,7 +18,7 @@
   val events = new Mutator_Event.Bus
 
   private var _mutators : List[Mutator.Info] = Nil
-  def apply() = _mutators
+  def apply(): List[Mutator.Info] = _mutators
   def apply(mutators: List[Mutator.Info])
   {
     _mutators = mutators