- don't check signature if the file is empty (valgrind reports with test

  001), thx Tony for the head up

Author: pierrejoye

ext/gd/libgd/gd_png.c

@@ -131,7 +131,10 @@ gdImagePtr gdImageCreateFromPngCtx (gdIOCtx * infile)
 	  /* first do a quick check that the file really is a PNG image; could
 	   * have used slightly more general png_sig_cmp() function instead
 	   */
-	gdGetBuf(sig, 8, infile);
+	if (gdGetBuf(sig, 8, infile) < 8) {
+		return NULL;
+	}
+
 	if (!png_check_sig (sig, 8)) { /* bad signature */
 		return NULL;
 	}