lavfi: handle NULL lists in avfilter_make_format_list

libavfilter/avfilter.h

@@ -27,7 +27,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  2
 #define LIBAVFILTER_VERSION_MINOR 14
-#define LIBAVFILTER_VERSION_MICRO  0
+#define LIBAVFILTER_VERSION_MICRO  1
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \
@@ -233,7 +233,8 @@ typedef struct AVFilterFormats {
  * Create a list of supported formats. This is intended for use in
  * AVFilter->query_formats().
  *
- * @param fmts list of media formats, terminated by -1
+ * @param fmts list of media formats, terminated by -1. If NULL an
+ *        empty list is created.
  * @return the format list, with no existing references
  */
 AVFilterFormats *avfilter_make_format_list(const int *fmts);

libavfilter/formats.c

@@ -73,15 +73,18 @@ AVFilterFormats *avfilter_merge_formats(AVFilterFormats *a, AVFilterFormats *b)
 AVFilterFormats *avfilter_make_format_list(const int *fmts)
 {
     AVFilterFormats *formats;
-    int count;
+    int count = 0;
 
-    for (count = 0; fmts[count] != -1; count++)
+    if (fmts)
-        ;
+        for (count = 0; fmts[count] != -1; count++)
+            ;
 
     formats               = av_mallocz(sizeof(AVFilterFormats));
-    formats->formats      = av_malloc(sizeof(*formats->formats) * count);
     formats->format_count = count;
-    memcpy(formats->formats, fmts, sizeof(*formats->formats) * count);
+    if (count) {
+        formats->formats  = av_malloc(sizeof(*formats->formats) * count);
+        memcpy(formats->formats, fmts, sizeof(*formats->formats) * count);
+    }
 
     return formats;
 }