fftools/ffprobe: fix print_dynamic_hdr_vivid

Don't print tone_mapping_param_num if tone_mapping_mode_flag is
disabled.

Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>

fftools/ffprobe.c

@@ -2221,8 +2221,8 @@ static void print_dynamic_hdr_vivid(WriterContext *w, const AVDynamicHDRVivid *m
         const AVHDRVividColorTransformParams *params = &metadata->params[n];
 
         print_int("tone_mapping_mode_flag", params->tone_mapping_mode_flag);
-        print_int("tone_mapping_param_num", params->tone_mapping_param_num);
         if (params->tone_mapping_mode_flag) {
+            print_int("tone_mapping_param_num", params->tone_mapping_param_num);
             for (int i = 0; i < params->tone_mapping_param_num; i++) {
                 const AVHDRVividColorToneMappingParams *tm_params = &params->tm_params[i];