zero percentage value shown as white and without arrow

to be consistent with the format if Statement of Asset.
(0% was previously green with top arrow)

name.abuchen.portfolio.ui/src/name/abuchen/portfolio/ui/util/viewers/NumberColorLabelProvider.java

@@ -32,7 +32,7 @@ public NumberColorLabelProvider(Values<N> format, Function<Object, N> label, Fun
     public Color getForeground(Object element)
     {
         Number value = label.apply(element);
-        if (value == null)
+        if (value == null || value.doubleValue() == 0)
             return null;
 
         return value.doubleValue() >= 0 ? Colors.theme().greenForeground() : Colors.theme().redForeground();
@@ -42,7 +42,7 @@ public Color getForeground(Object element)
     public Image getImage(Object element)
     {
         Number value = label.apply(element);
-        if (value == null)
+        if (value == null || value.doubleValue() == 0)
             return null;
 
         return value.doubleValue() >= 0 ? Images.GREEN_ARROW.image() : Images.RED_ARROW.image();