Index: trunk/src/org/openstreetmap/josm/gui/layer/LayerPositionStrategy.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/layer/LayerPositionStrategy.java	(revision 11007)
+++ trunk/src/org/openstreetmap/josm/gui/layer/LayerPositionStrategy.java	(revision 11008)
@@ -55,11 +55,14 @@
     static LayerPositionStrategy inFrontOfFirst(final Predicate<Layer> what) {
         return manager -> {
-            List<Layer> layers = manager.getLayers();
-            for (int i = 0; i < layers.size(); i++) {
-                if (what.test(layers.get(i))) {
-                    return i;
+            if (manager != null) {
+                List<Layer> layers = manager.getLayers();
+                for (int i = 0; i < layers.size(); i++) {
+                    if (what.test(layers.get(i))) {
+                        return i;
+                    }
                 }
+                return layers.size();
             }
-            return layers.size();
+            return 0;
         };
     }
@@ -72,8 +75,10 @@
     static LayerPositionStrategy afterLast(final Predicate<Layer> what) {
         return manager -> {
-            List<Layer> layers = manager.getLayers();
-            for (int i = layers.size() - 1; i >= 0; i--) {
-                if (what.test(layers.get(i))) {
-                    return i + 1;
+            if (manager != null) {
+                List<Layer> layers = manager.getLayers();
+                for (int i = layers.size() - 1; i >= 0; i--) {
+                    if (what.test(layers.get(i))) {
+                        return i + 1;
+                    }
                 }
             }
Index: trunk/test/unit/org/openstreetmap/josm/gui/layer/LayerPositionStrategyTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/gui/layer/LayerPositionStrategyTest.java	(revision 11008)
+++ trunk/test/unit/org/openstreetmap/josm/gui/layer/LayerPositionStrategyTest.java	(revision 11008)
@@ -0,0 +1,21 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.gui.layer;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+/**
+ * Test the {@link LayerPositionStrategy} class.
+ */
+public class LayerPositionStrategyTest {
+
+    /**
+     * Test of robustness against null manager.
+     */
+    @Test
+    public void testNullManager() {
+        assertEquals(0, LayerPositionStrategy.inFrontOfFirst(l -> true).getPosition(null));
+        assertEquals(0, LayerPositionStrategy.afterLast(l -> true).getPosition(null));
+    }
+}