Fix parallel parsing of POV demos

[saul]

Fixes #92

[github-actions]

BenchmarkDotNet v0.13.9+228a464e8be6c580ad9408e98f18813f6407fb5a, Ubuntu 22.04.5 LTS (Jammy Jellyfish)
AMD EPYC 7763, 1 CPU, 4 logical and 2 physical cores
.NET SDK 8.0.401
  [Host]     : .NET 8.0.8 (8.0.824.36612), X64 RyuJIT AVX2
  Job-BUWVAI : .NET 8.0.8 (8.0.824.36612), X64 RyuJIT AVX2
  Job-RFNEKJ : .NET 8.0.8 (8.0.824.36612), X64 RyuJIT AVX2

InvocationCount=1  MaxIterationCount=16  UnrollFactor=1  
WarmupCount=1  

Method	Job	BuildConfiguration	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
ParseDemo	Job-BUWVAI	Baseline	2.304 s	0.0150 s	0.0133 s	1.00	0.00	5000.0000	1000.0000	516 MB	1.00
ParseDemo	Job-RFNEKJ	Default	2.249 s	0.0107 s	0.0090 s	0.98	0.00	5000.0000	1000.0000	516 MB	1.00
ParseDemoParallel	Job-BUWVAI	Baseline	1.202 s	0.0197 s	0.0165 s	1.00	0.00	6000.0000	1000.0000	558.48 MB	1.00
ParseDemoParallel	Job-RFNEKJ	Default	1.209 s	0.0245 s	0.0217 s	1.01	0.03	6000.0000	1000.0000	558.49 MB	1.00