1767 return empty plot when observed data without nonZero values (#1768)

* initial implementation

* code review change

* test corrected

src/OSPSuite.Presentation/Presenters/SimulationPredictedVsObservedChartPresenter.cs

@@ -50,6 +50,11 @@ protected override void UpdateAnalysis()
 
          _identityRepositories.AddRange(_predictedVsObservedChartService.AddIdentityCurves(observationColumns, Chart));
 
+         //if no identity repository has been added, resulting in the chart not having been initialized, just return an empty plot
+         //this has been the case for having only one plot with exclusively 0 values
+         if (!_identityRepositories.Any())
+            return;
+
          if (ChartIsBeingCreated)
             _predictedVsObservedChartService.ConfigureAxesDimensionAndTitle(observationColumns, Chart);
 

tests/OSPSuite.Presentation.Tests/Presentation/SimulationPredictedVsObservedChartPresenterSpecs.cs

@@ -141,6 +141,8 @@ protected override void Context()
          _calculationData.Add(_concentrationDataColumn);
          A.CallTo(() => _observedDataRepository.AllObservedDataUsedBy(A<ISimulation>._)).Returns(new List<DataRepository>() { _calculationData });
 
+         A.CallTo(() => _predictedVsObservedService.AddIdentityCurves(A<List<DataColumn>>._, _predictedVsObservedChart)).Returns(new List<DataRepository>() { DomainHelperForSpecs.ObservedData() });
+
          sut.InitializeAnalysis(_predictedVsObservedChart);
       }
    }