Deal with 0-count substrings

[dandanlen]

The substringsCount can have members with Count == 0. I guess this happens when there are substrings that are suppressed. This is the cause of the following error.

Explorer.ExplorerException: Error in column exploration for `Clinic` / `prescriptions` / `dosage`.
 ---> System.ArgumentOutOfRangeException: max must be > min! (Parameter 'max')
   at Explorer.Common.RandomExtensions.NextLong(Random random, Int64 min, Int64 max) in /build/src/explorer/Common/RandomExtensions.cs:line 18
   at Explorer.Components.TextGeneratorComponent.GenerateString(SubstringsData substrings, Int32 minLength, Random rand) in /build/src/explorer/Components/TextGeneratorComponent.cs:line 79
   at System.Linq.Enumerable.SelectRangeIterator`1.ToList()
   at Explorer.Components.TextGeneratorComponent.Explore() in /build/src/explorer/Components/TextGeneratorComponent.cs:line 71
   at Explorer.Components.ExplorerComponent`1.<get_ResultAsync>b__2_0() in /build/src/explorer/Components/ExplorerComponent.cs:line 10
   at Explorer.Components.TextGeneratorComponent.YieldMetrics()+MoveNext() in /build/src/explorer/Components/TextGeneratorComponent.cs:line 49
   at Explorer.Components.TextGeneratorComponent.YieldMetrics()+System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult()
   at Explorer.Components.PublisherComponent.PublishMetrics(MetricsPublisher publisher) in /build/src/explorer/Components/PublisherComponent.cs:line 14
   at Explorer.Components.PublisherComponent.PublishMetrics(MetricsPublisher publisher) in /build/src/explorer/Components/PublisherComponent.cs:line 14
   at Explorer.ColumnExploration.<RunTask>b__13_0(Task t) in /build/src/explorer/ColumnExploration.cs:line 60

[sentry-io[bot]]

Sentry issue: EXPLORER-2N

[sentry-io[bot]]

Sentry issue: EXPLORER-2J