System.ArgumentNullException: Value cannot be null. (Parameter 'key')

**Describe the bug**
I recently downloaded full-win-20.8.1.0, and running DEXTER against Saas AppD Controller, it detects I have 20.8.0.0 and prompts accordingly:
"Latest released version is 20.8.1.0, and yours is 20.8.0.0. Would you like to upgrade (y/n)?". So how do I get a copy of 20.8.1.0 ?

Also, when running Jobfile with Target.Type="APM" I get the following error:

System.ArgumentNullException: Value cannot be null. (Parameter 'key')
at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
at System.Collections.Generic.Dictionary`2.TryGetValue(TKey key, TValue& value)
at AppDynamics.Dexter.ProcessingSteps.IndexAPMMetricsList.Execute(ProgramOptions programOptions, JobConfiguration jobConfiguration) in C:\Users\bhjel\RiderProjects\AppDynamics.DEXTER\ProcessingSteps\Index\IndexAPMMetricsList.cs:line 855

How do I address this error?

**Expected behavior**
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**Desktop (please complete the following information):**
- OS: [e.g. iOS]
- .NET Framework Type (Full/Core)
- .NET/.NET Core Framework Version

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Start with ProcessingSteps/Index/IndexAPMMetricsList.cs around line 855 and inspect the APM Jobfile inputs that lead to the null dictionary key. Reproduce the failure with Target.Type="APM" and verify that the job completes without the ArgumentNullException; the report-version question is also unresolved in this issue.

Written by the indexing model from the issue text.