Truth plot does not reappear when it should for certain forecaster

[kateharwood]

At times, truth plot does not reappear when it should after not having data for selected forecasters. So far have only seen this with imperial-ensemble2.

1. Select imperial-ensemble2 and another forecaster (like the baseline)
2. Select location AK
3. Remove other forecaster so just imperial-ensemble2 is selected. There is no data, so no plot - fine, the error message shows up.
4. Change location to US (which this forecaster does have data for). Observe that truth plot is still gone. If you choose this forecaster and US directly on dashboard load, we see a truth plot.