Index: trunk/src/org/openstreetmap/josm/gui/mappaint/styleelement/NodeElement.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/styleelement/NodeElement.java	(revision 10239)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/styleelement/NodeElement.java	(revision 10240)
@@ -23,4 +23,5 @@
 import org.openstreetmap.josm.gui.mappaint.styleelement.BoxTextElement.SimpleBoxProvider;
 import org.openstreetmap.josm.gui.util.RotationAngle;
+import org.openstreetmap.josm.tools.CheckParameterUtil;
 import org.openstreetmap.josm.tools.Utils;
 
@@ -79,4 +80,6 @@
     }
 
+    private static final String[] ICON_KEYS = {ICON_IMAGE, ICON_WIDTH, ICON_HEIGHT, ICON_OPACITY, ICON_OFFSET_X, ICON_OFFSET_Y};
+
     public static final NodeElement SIMPLE_NODE_ELEMSTYLE;
     public static final BoxProvider SIMPLE_NODE_ELEMSTYLE_BOXPROVIDER;
@@ -92,6 +95,4 @@
     public static final StyleElementList DEFAULT_NODE_STYLELIST_TEXT = new StyleElementList(NodeElement.SIMPLE_NODE_ELEMSTYLE,
             BoxTextElement.SIMPLE_NODE_TEXT_ELEMSTYLE);
-
-    private static final String[] ICON_KEYS = {ICON_IMAGE, ICON_WIDTH, ICON_HEIGHT, ICON_OPACITY, ICON_OFFSET_X, ICON_OFFSET_Y};
 
     protected NodeElement(Cascade c, MapImage mapImage, Symbol symbol, float defaultMajorZindex, RotationAngle rotationAngle) {
@@ -144,4 +145,7 @@
 
     public static MapImage createIcon(final Environment env, final String[] keys) {
+        CheckParameterUtil.ensureParameterNotNull(env, "env");
+        CheckParameterUtil.ensureParameterNotNull(keys, "keys");
+
         Cascade c = env.mc.getCascade(env.layer);