avfilter/ass: make sure the log level are in available range

libavfilter/vf_subtitles.c

@@ -80,7 +80,9 @@ static const int ass_libavfilter_log_level_map[] = {
 
 static void ass_log(int ass_level, const char *fmt, va_list args, void *ctx)
 {
-    int level = ass_libavfilter_log_level_map[ass_level];
+    const int ass_level_clip = av_clip(ass_level, 0,
+        FF_ARRAY_ELEMS(ass_libavfilter_log_level_map) - 1);
+    const int level = ass_libavfilter_log_level_map[ass_level_clip];
 
     av_vlog(ctx, level, fmt, args);
     av_log(ctx, level, "\n");