avcodec: make avcodec_close() more tolerant.

See previous commit.

doc/APIchanges

@@ -15,6 +15,9 @@ libavutil:     2012-10-22
 
 API changes, most recent first:
 
+2013-xx-xx - xxxxxxx - lavc 55.31.101 - avcodec.h
+  avcodec_close() argument can be NULL.
+
 2013-xx-xx - xxxxxxx - lavf 55.16.101 - avformat.h
   avformat_close_input() argument can be NULL and point on NULL.
 

libavcodec/utils.c

@@ -2398,7 +2398,12 @@ av_cold int ff_codec_close_recursive(AVCodecContext *avctx)
 
 av_cold int avcodec_close(AVCodecContext *avctx)
 {
-    int ret = ff_lock_avcodec(avctx);
+    int ret;
+
+    if (!avctx)
+        return 0;
+
+    ret = ff_lock_avcodec(avctx);
     if (ret < 0)
         return ret;
 

libavcodec/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVCODEC_VERSION_MAJOR 55
 #define LIBAVCODEC_VERSION_MINOR  31
-#define LIBAVCODEC_VERSION_MICRO 100
+#define LIBAVCODEC_VERSION_MICRO 101
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \