ffb: Silence compiler warnings.

src/mesa/drivers/dri/ffb/ffb_tris.c

@@ -352,7 +352,7 @@ static struct {
 #define LOCAL_VARS(n)				\
    ffbContextPtr fmesa = FFB_CONTEXT(ctx);	\
    __DRIdrawablePrivate *dPriv = fmesa->driDrawable; \
-   ffb_color color[n];				\
+   ffb_color color[n] = { { 0 } };		\
    (void) color; (void) dPriv;
 
 /***********************************************************************