This has some bug while parsing through pipeline activities to find the dependency pipelines

Function pipelineSortUtil has the issue at line 80 & 81. Error is as below
one of the pipeline is leading to succeed the condition at line 43 (if ($activity.Pipeline) ) and then failing at the below code. Pls check and fix it.
"
$pipeline.Activities | ForEach-Object { getPipelineDependencies -activity $_ -pipelineNameResourceDict $pipelineNameResourceDict } | ForEach-Object {
pipelineSortUtil -pipeline $pipelineNameResourceDict[$_] -pipelineNameResourceDict $pipelineNameResourceDict -visited $visited -sortedList $sortedList
}
"

Error:
Line |
32 | pipelineSortUtil -pipeline $pipelineNameResourceDict[$_] -pip …
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| Index operation failed; the array index evaluated to null.