fix NPE in viewimage

Caused by: java.lang.NullPointerException
	at net.yacy.peers.graphics.EncodedImage.<init>(EncodedImage.java:73)
	at ViewImage.respond(ViewImage.java:156)

htroot/ViewImage.java

@@ -152,9 +152,11 @@ public class ViewImage {
             
             // read image
             image = ImageParser.parse(urlString, imgb);
-
-            if (image == null || (auth && (width == 0 || height == 0) && maxwidth == 0 && maxheight == 0)) return ext == null ? image : new EncodedImage(image, ext, isStatic);
-
+            if (image == null) {
+                return null;
+            } else {
+                if ((auth && (width == 0 || height == 0) && maxwidth == 0 && maxheight == 0)) return ext == null ? image : new EncodedImage(image, ext, isStatic);
+            }
             // find original size
             final int h = image.getHeight(null);
             final int w = image.getWidth(null);