Collected Vespene score remains 0 during the whole match

Hello there,

I've been trying to use this API and wanted to register every 10 seconds the current scores of the player.
When I use the following code on the OnStep() method
```
const sc2::ObservationInterface* obs = Observation();
const struct sc2::Score& score = obs->GetScore();
std::cout << "> collected_minerals - " << score.score_details.collected_minerals << std::endl;
std::cout << "> collected_vespene - " << score.score_details.collected_vespene << std::endl;
```
for some reason `collected_vespene` remains 0 during the whole match but every other score updates consistently (strangely enough, when a player starts collecting vespene gas the score `score.score_details.collection_rate_vespene` will update correctly).

I wrote me code directly expanding the replay.cc example.

Thank you.