Avoid a possible overflow when reading Nikon avi files.

Suggested-by: Reimar

libavformat/avidec.c

@@ -350,8 +350,7 @@ static void avi_read_nikon(AVFormatContext *s, uint64_t end)
                 uint16_t size    = avio_rl16(s->pb);
                 const char *name = NULL;
                 char buffer[64]  = { 0 };
-                if (avio_tell(s->pb) + size > tag_end)
-                    size = tag_end - avio_tell(s->pb);
+                size = FFMIN(size, tag_end - avio_tell(s->pb));
                 size -= avio_read(s->pb, buffer,
                                   FFMIN(size, sizeof(buffer) - 1));
                 switch (tag) {