I submitted this idea in the older 'suggestion' application several year ago and I don't want it to get lost. The best way to describe this is by showing the actual series datasource:
Note that the timeline is 'banded' every minute and only 4 (in this screenshot) had actual observations (datapoints). Normally if there are only a few null points in the series array, the igDatachart (line or area) will correctly show a gap indicating no data, as opposed to hiding this gap by connecting to the next data point. However in this case, the chart line/area will render nothing. This is incorrect as there was actually data in that time range.
This is actually a known limitation of many chart vendors and was pointed out by a Data Visualization expert Stephen Few in a blog post:
Page 3 of this blog illustrates this point.