List index out of bounds error when `Allow_Flow_Recursion__c` is true.

[mitchspano]

Expected Behavior

We should be able to invoke flows recursively using the Allow_Flow_Recursion__c checkbox on the Trigger Action metadata

Actual Behavior

System.ListException: List index out of bounds: 0

Class.TriggerActionFlow.handleInvocableResults: line 265, column 1
Class.TriggerActionFlow.afterUpdate: line 113, column 1
Class.MetadataTriggerHandler.executeActions: line 246, column 1
Class.MetadataTriggerHandler.afterUpdate: line 67, column 1
Class.TriggerBase.run: line 84, column 1
Trigger.OpportunityTrigger: line 10, column 1

Steps to Reproduce the Problem

1. Create a flow which recursively updates the same record
2. Enable that flow using the Trigger Actions Framework
3. Edit a record which induces recursive flow execution