NUnit serialization fails with out of bound index

[BernieWhite]

Description of the issue

NUnit serialization fails when returning results for object that where not processed by any rule.

To Reproduce

Steps to reproduce the issue:

Assert-PSRule -InputPath out/templates/*.json -Path ./.rules/ -OutputPath reports/ps-rule-unit.xml -OutputFormat NUnit3;

Expected behaviour

Serialization should ignore results from objects that were not processed.

Error output

Index was outside the bounds of the array.
At C:\<removed>\PSRule\PSRule.psm1:513 char:17
+                 $pipeline.End();
+                 ~~~~~~~~~~~~~~~
+ CategoryInfo          : OperationStopped: (:) [], IndexOutOfRangeException
+ FullyQualifiedErrorId : System.IndexOutOfRangeException

Module in use and version:

• Module: PSRule
• Version: 0.11.0

Captured output from $PSVersionTable:

Name                           Value
----                           -----
PSVersion                      6.2.3
PSEdition                      Core
GitCommitId                    6.2.3
OS                             Microsoft Windows 10.0.18363
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0