Changed the Image so that the actual contained image may be null.

+ Changed the constructor to no longer throw a BuildException if the image from the builder is null.
+ Changed the paint method to check for an update of the image from the informationProvider before the null check for the image field is made to give the image a fighting change to be loaded.

TULIP/src/lu/list/itis/dkd/tui/widget/corona/Image.java

@@ -55,12 +55,7 @@ public class Image extends Corona implements ContextEventListener, InformationRe
      */
     public Image(ImageBuilder builder) throws BuildException {
         super(builder);
-        // TODO look if image can be null or not
-        if (builder.image != null) {
-            image = builder.image;
-        } else {
-            throw new BuildException("The image may not be null!"); //$NON-NLS-1$
-        }
+        image = builder.image;
         informationProvider = builder.informationProvider;
     }
 
@@ -72,6 +67,10 @@ public class Image extends Corona implements ContextEventListener, InformationRe
      */
     @Override
     public void paint(Graphics2D canvas) {
+        if (image == null) {
+            image = informationProvider == null ? image : informationProvider.getInformation();
+        }
+
         if (!active || image == null) {
             return;
         }
@@ -96,8 +95,6 @@ public class Image extends Corona implements ContextEventListener, InformationRe
 
         rotation.transform(new Point(), drawAt);
 
-        image = informationProvider == null ? image : informationProvider.getInformation();
-
         if (Double.compare(initialRotation, 0d) != 0) {
             AffineTransform transformation = new AffineTransform();
             transformation.rotate(initialRotation, spinOnCoronaCentre ? drawAt.getX() + image.getWidth(null) / 2 : drawAt.getX(), spinOnCoronaCentre ? drawAt.getY() + image.getHeight(null) / 2 : drawAt.getY());