Make avfilter_graph_free() do nothing if graph is NULL.

Originally committed as revision 26323 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavfilter/avfilter.h

@@ -28,7 +28,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  1
 #define LIBAVFILTER_VERSION_MINOR 73
-#define LIBAVFILTER_VERSION_MICRO  0
+#define LIBAVFILTER_VERSION_MICRO  1
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/avfiltergraph.c

@@ -34,6 +34,8 @@ AVFilterGraph *avfilter_graph_alloc(void)
 
 void avfilter_graph_free(AVFilterGraph *graph)
 {
+    if (!graph)
+        return;
     for (; graph->filter_count > 0; graph->filter_count --)
         avfilter_free(graph->filters[graph->filter_count - 1]);
     av_freep(&graph->scale_sws_opts);

libavfilter/avfiltergraph.h

@@ -79,7 +79,7 @@ int avfilter_graph_create_filter(AVFilterContext **filt_ctx, AVFilter *filt,
 int avfilter_graph_config(AVFilterGraph *graphctx, AVClass *log_ctx);
 
 /**
- * Free a graph and destroy its links.
+ * Free a graph and destroy its links, graph may be NULL.
  */
 void avfilter_graph_free(AVFilterGraph *graph);