decoder: fix potential NULL dereference

src/input/decoder.c

@@ -1065,8 +1065,11 @@ static void DecoderFixTs( decoder_t *p_dec, mtime_t *pi_ts0, mtime_t *pi_ts1,
         if( pi_ts1 && *pi_ts1 > VLC_TS_INVALID )
             *pi_ts1 += i_es_delay;
         if( input_clock_ConvertTS( p_clock, &i_rate, pi_ts0, pi_ts1, i_ts_bound ) ) {
-            msg_Err(p_dec, "Could not convert timestamps %"PRId64", %"PRId64"",
-                    *pi_ts0, *pi_ts1);
+            if( pi_ts1 != NULL )
+                msg_Err(p_dec, "Could not convert timestamps %"PRId64
+                        ", %"PRId64"", *pi_ts0, *pi_ts1);
+            else
+                msg_Err(p_dec, "Could not convert timestamp %"PRId64, *pi_ts0);
             *pi_ts0 = VLC_TS_INVALID;
         }
     }