Metrics dashboard doesn't show an empty state on the NGINX VTS exporter group due to NaN values in the result

Currently monitoring dashboards show an empty state when a panel doesn't have enough data to render a chart.

The bug itself resides in just the NGINX VTS exporter, due to the HTTP error query as it doesn't show the empty state even though there is not data to display

Update from 2019-12-13, the latency panel is the one that shows the empty graph now

Downloaded dataset (CSV):

timestamp,Latency (ms)
2020-01-15T15:33:12.000Z,NaN
2020-01-15T15:50:00.000Z,NaN
2020-01-15T16:06:48.000Z,NaN
2020-01-15T16:23:36.000Z,NaN
2020-01-15T16:40:24.000Z,NaN
2020-01-15T16:57:12.000Z,NaN
2020-01-15T17:14:00.000Z,NaN
2020-01-15T17:30:48.000Z,NaN
2020-01-15T17:47:36.000Z,NaN
2020-01-15T18:04:24.000Z,NaN
2020-01-15T18:21:12.000Z,NaN
2020-01-15T18:38:00.000Z,NaN
2020-01-15T18:54:48.000Z,NaN
2020-01-15T19:11:36.000Z,NaN
2020-01-15T19:28:24.000Z,NaN
2020-01-15T19:45:12.000Z,NaN
2020-01-15T20:02:00.000Z,NaN
2020-01-15T20:18:48.000Z,NaN
2020-01-15T20:35:36.000Z,NaN
2020-01-15T20:52:24.000Z,NaN
2020-01-15T21:09:12.000Z,NaN

Possible solutions

It appears we are not filtering out the NaN values that we get in the request. We should filter them out from our results.