Fix possible memory leak in art_render_new.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit 3d29aa4f85)

src/art_render.c

@@ -48,9 +48,6 @@ art_render_new (int x0, int y0, int x1, int y1,
   ArtRenderPriv *priv;
   ArtRender *result;
 
-  priv = art_new (ArtRenderPriv, 1);
-  result = &priv->super;
-
   if (n_chan > ART_MAX_CHAN)
     {
       art_warn ("art_render_new: n_chan = %d, exceeds %d max\n",
@@ -68,6 +65,10 @@ art_render_new (int x0, int y0, int x1, int y1,
       art_warn ("art_render_new: x0 >= x1 (x0 = %d, x1 = %d)\n", x0, x1);
       return NULL;
     }
+
+  priv = art_new (ArtRenderPriv, 1);
+  result = &priv->super;
+
   result->x0 = x0;
   result->y0 = y0;
   result->x1 = x1;