Index: applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/CadastreGrabber.java
===================================================================
--- applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/CadastreGrabber.java	(revision 33391)
+++ applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/CadastreGrabber.java	(revision 33392)
@@ -32,4 +32,6 @@
                 url = getURLVector(lambertMin, lambertMax);
             BufferedImage img = grab(url);
+            if (img == null)
+                throw new OsmTransferException(url.toString());
             ImageModifier imageModified;
             if (wmsLayer.isRaster())
@@ -37,5 +39,5 @@
             else
                 imageModified = new VectorImageModifier(img, false);
-            return new GeorefImage(imageModified.bufferedImage, lambertMin, lambertMax, wmsLayer);
+            return new GeorefImage(imageModified.getBufferedImage(), lambertMin, lambertMax, wmsLayer);
         } catch (MalformedURLException e) {
             throw (IOException) new IOException(tr("CadastreGrabber: Illegal url.")).initCause(e);
Index: applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/GeorefImage.java
===================================================================
--- applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/GeorefImage.java	(revision 33391)
+++ applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/GeorefImage.java	(revision 33392)
@@ -17,4 +17,5 @@
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
+import java.util.Objects;
 
 import javax.imageio.ImageIO;
@@ -46,8 +47,8 @@
 
     public GeorefImage(BufferedImage img, EastNorth min, EastNorth max, WMSLayer wmsLayer) {
-        image = img;
-
-        this.min = min;
-        this.max = max;
+        image = Objects.requireNonNull(img);
+
+        this.min = Objects.requireNonNull(min);
+        this.max = Objects.requireNonNull(max);
         this.orgRaster[0] = min;
         this.orgRaster[1] = new EastNorth(min.east(), max.north());
Index: applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/ImageModifier.java
===================================================================
--- applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/ImageModifier.java	(revision 33391)
+++ applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/ImageModifier.java	(revision 33392)
@@ -8,4 +8,5 @@
 import java.awt.image.DataBuffer;
 import java.awt.image.IndexColorModel;
+import java.util.Objects;
 
 public abstract class ImageModifier {
@@ -17,5 +18,5 @@
     protected int parcelColor = Color.RED.getRGB();
 
-    public BufferedImage bufferedImage;
+    protected BufferedImage bufferedImage;
 
     public static int[] cRoofColors = new int[] {-197380, -592138};
@@ -160,3 +161,18 @@
     }
 
+    /**
+     * Returns the buffered image.
+     * @return the buffered image
+     */
+    public final BufferedImage getBufferedImage() {
+        return bufferedImage;
+    }
+
+    /**
+     * Sets the buffered image.
+     * @param bufferedImage the buffered image
+     */
+    protected final void setBufferedImage(BufferedImage bufferedImage) {
+        this.bufferedImage = Objects.requireNonNull(bufferedImage);
+    }
 }
Index: applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/RasterImageModifier.java
===================================================================
--- applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/RasterImageModifier.java	(revision 33391)
+++ applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/RasterImageModifier.java	(revision 33392)
@@ -18,5 +18,5 @@
 
     public RasterImageModifier(BufferedImage bi) {
-        bufferedImage = bi;
+        setBufferedImage(bi);
         transparencyEnabled = Main.pref.getBoolean("cadastrewms.backgroundTransparent");
         if (transparencyEnabled)
@@ -84,5 +84,5 @@
                 }
             }
-            bufferedImage = bi;
+            setBufferedImage(bi);
         }
         return;
Index: applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/VectorImageModifier.java
===================================================================
--- applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/VectorImageModifier.java	(revision 33391)
+++ applications/editors/josm/plugins/cadastre-fr/src/cadastre_fr/VectorImageModifier.java	(revision 33392)
@@ -24,5 +24,5 @@
 
     public VectorImageModifier(BufferedImage bi, boolean monocolor) {
-        bufferedImage = bi;
+        setBufferedImage(bi);
         if (Main.pref.getBoolean("cadastrewms.backgroundTransparent"))
             makeTransparent();
@@ -32,5 +32,5 @@
             invertGrey();
         if (monocolor)
-            bufferedImage = convert8(convert4(bufferedImage));
+            setBufferedImage(convert8(convert4(bufferedImage)));
     }
 
@@ -107,5 +107,5 @@
             IndexColorModel icm2 = new IndexColorModel(colorModel.getPixelSize(), size, reds, greens, blues,
                     backgroundPixel);
-            bufferedImage = new BufferedImage(icm2, raster, bufferedImage.isAlphaPremultiplied(), null);
+            setBufferedImage(new BufferedImage(icm2, raster, bufferedImage.isAlphaPremultiplied(), null));
         }
         return;