ff_add_index_entry: reject AV_NOPTS_VALUE

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -1573,6 +1573,9 @@ int ff_add_index_entry(AVIndexEntry **index_entries,
     if((unsigned)*nb_index_entries + 1 >= UINT_MAX / sizeof(AVIndexEntry))
         return -1;
 
+    if(timestamp == AV_NOPTS_VALUE)
+        return AVERROR(EINVAL);
+
     if (is_relative(timestamp)) //FIXME this maintains previous behavior but we should shift by the correct offset once known
         timestamp -= RELATIVE_TS_BASE;