a size like QSize(10,0) is valid but will end up in a null pixmap, and

this thing did confuse the cache a lot
CCBUG: 177172
does this patch fixes it? will keep open a day to be really sure :)

svn path=/trunk/KDE/kdelibs/; revision=894591

svg.cpp

@@ -155,7 +155,7 @@ class SvgPrivate
                 size = elementRect(elementId).size().toSize();
             }
 
-            if (!size.isValid()) {
+            if (size.width() <= 0 || size.height() <= 0) {
                 return QPixmap();
             }