Standard deviation as 0

[CarenD]

We continue to have a problem with the core not allowing standard deviation values of 0.
2020-06-08 14:25:08,728 - Internal error occurred within the program:
2020-06-08 14:25:08,736 - Given parameter (or parameters) are not valid.
Parameter name: Sigma
2020-06-08 14:25:08,736 -
2020-06-08 14:25:08,738 - Stack trace:
2020-06-08 14:25:08,899 - at Troschuetz.Random.Distributions.Continuous.NormalDistribution.set_Sigma(Double value) in C:\projects\troschuetz-random\src\Troschuetz.Random\Distributions\Continuous\NormalDistribution.cs:line 158
at Landis.Extension.Succession.ForC.SpeciesData.GenerateNewANPPandMaxBiomass(Int32 years, Int32 spinupyear)
at Landis.Extension.Succession.ForC.SpeciesData.Initialize(IInputParameters parameters)
at Landis.Extension.Succession.ForC.PlugIn.Initialize()
at Landis.Model.Run(String scenarioPath, IUserInterface ui)
at Landis.App.Main(String[] args) in D:\CGAProjects\Rob\LANDIS_FINAL\GitHubRepo\Core-Model-v7\Tool-Console\src\App.cs:line 99