invalidate the image cache after downloading new images so the new images can be loaded if they were previously cached as not found

src/main/java/forge/ImageCache.java

@@ -83,6 +83,11 @@ public class ImageCache {
             e.printStackTrace();
         }
     }
+    
+    public static void clear() {
+        CACHE.invalidateAll();
+    }
+    
     /**
      * retrieve an image from the cache.  returns null if the image is not found in the cache
      * and cannot be loaded from disk.  pass -1 for width and/or height to avoid resizing in that dimension.

src/main/java/forge/gui/download/GuiDownloader.java

@@ -55,6 +55,7 @@ import org.apache.commons.lang3.tuple.Pair;
 import com.esotericsoftware.minlog.Log;
 
 import forge.Command;
+import forge.ImageCache;
 import forge.error.BugReporter;
 import forge.gui.SOverlayUtils;
 import forge.gui.toolbox.FButton;
@@ -70,12 +71,14 @@ import forge.util.MyRandom;
 
 @SuppressWarnings("serial")
 public abstract class GuiDownloader extends DefaultBoundedRangeModel implements Runnable {
-    public static final Proxy.Type[] TYPES = Proxy.Type.values(); /** */
+    public static final Proxy.Type[] TYPES = Proxy.Type.values();
 
     // Actions and commands
     private final ActionListener actStartDownload = new ActionListener() {
         @Override
         public void actionPerformed(final ActionEvent e) {
+            // invalidate image cache so newly downloaded images will be loaded
+            ImageCache.clear();
             new Thread(GuiDownloader.this).start();
             btnStart.setEnabled(false);
         }
@@ -374,5 +377,4 @@ public abstract class GuiDownloader extends DefaultBoundedRangeModel implements
             }
         }
     }
-
 }