Fix invalid free when preset file not found

https://bugs.gentoo.org/show_bug.cgi?id=322945

Author: Brennan Shacklett

diff -urN transcode-1.1.7-orig/export/export_ffmpeg.c transcode-1.1.7/export/export_ffmpeg.c

--- transcode-1.1.7-orig/export/export_ffmpeg.c	2011-11-19 08:50:27.000000000 -0800

+++ transcode-1.1.7/export/export_ffmpeg.c	2012-07-03 20:07:05.669083945 -0700

@@ -321,7 +321,7 @@

     }

     if(!f){

-        fprintf(stderr, "File for preset '%s' not found\n", arg);

+        tc_log_error(MOD_NAME, "File for preset '%s' not found", arg);

         av_exit(1);

     }

@@ -1207,7 +1207,7 @@

 	/* FIXME: transcode itself contains "broken ffmpeg default settings", thus we need to override them! */

 	if (lavc_param_video_preset) {

 		avcodec_opts[AVMEDIA_TYPE_VIDEO] = lavc_venc_context;

-		video_codec_name = ffmpeg_codec_name(codec->name);

+		video_codec_name = av_strdup(ffmpeg_codec_name(codec->name));

 		const char *preset_start = lavc_param_video_preset;

 		while (preset_start) {

@@ -1225,6 +1225,8 @@

 			if (opt_preset("vpre", preset_name) != 0) {

 				tc_log_warn(MOD_NAME, "Parsing ffmpeg preset '%s' failed", preset_name);

 			}

+      av_free(video_codec_name);

+      video_codec_name = NULL;

 			if (verbose) {

 				int i;

 				tc_log_info(MOD_NAME, "After parsing preset '%s', %i options are overridden:", preset_name, opt_name_count);