Finish off the previous fix for TFP.

A couple of those lines of debug printfs I deleted weren't actually debug
printfs.

src/glx/x11/dri2_glx.c

@@ -211,6 +211,9 @@ dri2GetBuffers(__DRIdrawable *driDrawable,
 
     buffers = DRI2GetBuffers(pdraw->base.psc->dpy, pdraw->base.xDrawable,
 			     width, height, attachments, count, out_count);
+    if (buffers == NULL)
+       return NULL;
+
     pdraw->width = *width;
     pdraw->height = *height;