Invalid SampleResult breaks Dashboard graphs that depend on Time

**UbikLoadPack support** ([Bug 62388](https://bz.apache.org/bugzilla//show_bug.cgi?id=62388&redirect=false)):
If for some reason a plugin generates a SampleResult where sampleStart was not called, timeStamp column will be 0 in CSV.

This will break the report leading to weird graphs.

Shouldn't there be a protection in JMeter against this by ignoring sampleresult with warning/error ?

In the case we face we have 4 samples in this case for 200000 correct sampleResults, as a consequence the graph is corrupt.

OS: All