avutil/timestamp: avoid possible FPE when 0 is passed to av_ts_make_time_string2()

Signed-off-by: Marton Balint <cus@passwd.hu>
(cherry picked from commit 0d5e3f5a40)

libavutil/timestamp.c

@@ -24,7 +24,7 @@ char *av_ts_make_time_string2(char *buf, int64_t ts, AVRational tb)
         snprintf(buf, AV_TS_MAX_STRING_SIZE, "NOPTS");
     } else {
         double val = av_q2d(tb) * ts;
-        double log = floor(log10(fabs(val)));
+        double log = (fpclassify(val) == FP_ZERO ? -INFINITY : floor(log10(fabs(val))));
         int precision = (isfinite(log) && log < 0) ? -log + 5 : 6;
         int last = snprintf(buf, AV_TS_MAX_STRING_SIZE, "%.*f", precision, val);
         last = FFMIN(last, AV_TS_MAX_STRING_SIZE - 1) - 1;