avformat/apetag: tag values are unsigned

Fixes: UBSan runtime error
Found-by: Clusterfuzz
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/apetag.c

@@ -29,7 +29,7 @@
 #include "apetag.h"
 #include "internal.h"
 
-#define APE_TAG_FLAG_CONTAINS_HEADER  (1 << 31)
+#define APE_TAG_FLAG_CONTAINS_HEADER  (1U << 31)
 #define APE_TAG_FLAG_LACKS_FOOTER     (1 << 30)
 #define APE_TAG_FLAG_IS_HEADER        (1 << 29)
 #define APE_TAG_FLAG_IS_BINARY        (1 << 1)