Index: trunk/src/org/openstreetmap/josm/gui/widgets/MultiSplitLayout.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/widgets/MultiSplitLayout.java	(revision 16439)
+++ trunk/src/org/openstreetmap/josm/gui/widgets/MultiSplitLayout.java	(revision 16440)
@@ -777,8 +777,8 @@
         } else if (root instanceof Split) {
             Split split = (Split) root;
-            return split.getChildren().stream()
-                    .filter(child -> child.getBounds().contains(x, y))
-                    .map(child -> dividerAt(child, x, y))
-                    .findFirst().orElse(null);
+            for (Node child : split.getChildren()) {
+                if (child.getBounds().contains(x, y))
+                    return dividerAt(child, x, y);
+            }
         }
         return null;