sna: Skip uploading unintialiased pixmap data

References: https://bugs.freedesktop.org/show_bug.cgi?id=47597
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/sna/sna_render.c

@@ -497,6 +497,9 @@ static struct kgem_bo *upload(struct sna *sna,
 
 	priv = sna_pixmap(pixmap);
 	if (priv) {
+		if (priv->cpu_damage == NULL)
+			return NULL;
+
 		/* As we know this box is on the CPU just fixup the shadow */
 		if (priv->mapped) {
 			pixmap->devPrivate.ptr = NULL;