DEXTER 21.8.0.0 crashes during IndexAPMEntities with ArgumentNullException on Controller 26.1.1.0

**Describe the bug**
DEXTER consistently fails during the entity indexing phase when DetectedEntities=true.

The failure occurs across multiple applications, so it does not appear to be application-specific.

The extraction phases complete successfully, including:

dashboards
metrics extraction
snapshots
configuration
events
policies

The failure occurs during indexing/report generation.

**To Reproduce**
Steps to reproduce the behavior:
1. Download and extract DEXTER 21.8.0.0.
2. Create or update job.json.
3. Open PowerShell.
4. Change directory to the DEXTER executable location:
cd C:\Users\\Downloads\full-win\bin\Publish\full-win
5. Execute the ETL job:
.\AppDynamics.DEXTER.exe -j job.json -v
6. Observe execution progress in console output and generated logs.

The issue occurs during:
Executing job step IndexAPMEntities(60)
DEXTER terminates with:
System.ArgumentNullException: Value cannot be null. (Parameter 'input')
at System.Text.RegularExpressions.Regex.Match(String input)
at AppDynamics.Dexter.ProcessingSteps.IndexAPMEntities.Execute(...)

**Expected behavior**
DEXTER completes indexing successfully
Spreadsheet/report generation completes

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Desktop (please complete the following information):**
OS: Windows 11
dotnet --info reports OS Version: 10.0.26200
.NET Framework Type: .NET Core
.NET/.NET Core Framework Version:
SDK: 9.0.305
Host: 10.0.5
Microsoft.NETCore.App runtimes installed:
6.0.15
6.0.16
7.0.5
7.0.7
7.0.11
8.0.3
8.0.14
9.0.9
10.0.5

DEXTER runtime observed in logs:

Framework: .NET Core 3.1.6

**Logs**

[AppDynamics.Dexter.Main.2026-05-20.redacted.log](https://github.com/user-attachments/files/28199197/AppDynamics.Dexter.Main.2026-05-20.redacted.log)
[AppDynamics.Dexter.Controller.2026-05-20(1).redacted.log](https://github.com/user-attachments/files/28199196/AppDynamics.Dexter.Controller.2026-05-20.1.redacted.log)
[AppDynamics.Dexter.Console.2026-05-20(1).redacted.log](https://github.com/user-attachments/files/28199198/AppDynamics.Dexter.Console.2026-05-20.1.redacted.log)

**Reports**
No reports being created

Start by reviewing the IndexAPMEntities execution path and the attached Main, Controller, and Console logs, focusing on the Regex.Match call that receives a null input. Reproduce the job with DetectedEntities=true using the documented PowerShell command; done means indexing completes and spreadsheet/report generation produces output without the ArgumentNullException.

Written by the indexing model from the issue text.