Jenkins Scripted Pipeline Singleton Null Pointer E

Question

I have recently started an effort to start consolidating some global variables that are set up for our Jenkins scripted pipeline. I am starting small (with a single boolean to control whether log a lot of "extra" stuff to the build log) and wanted to follow the NotificationConfig created by Szymon Stepniak. However, I am unable to get past a "NullPointerException" that is thrown during the initialization of the DebugOptions singleton.

Shared Library Source Layout

.
├── src
│   └── foo
│       └── utils
│           └── DebugOptions.groovy
└── vars
    ├── debugOptions.groovy
    └── standardPipeline.groovy

src/com/foo/utils/DebugOptions.groovy

#!/usr/bin/env groovy
package com.foo.utils;

@Singleton
class DebugOptions {
    // Simple wrapper around a debugging options to prevent argument 
    // explosion for everything that needs to filter output.
    boolean flag = false
}

vars/debugOptions.groovy

#!groovy
import com.foo.utils.DebugOptions
// This DSL ("Domain Specific Language") helps modify and manage configuration objects
// Implement a closure body to be executed in context of DebugOptions
// Defining in vars makes it globally accessible
// 
// Inspired by code at:
// https://stackoverflow.com/questions/50962643/best-way-to-set-reusable-property-in-jenkinsfile
def call(body) {
    body.resolveStrategy = Closure.DELEGATE_FIRST
    body.delegate = DebugOptions.instance
    body()
}

/vars/standardPipeline.groovy

#!/usr/bin/env groovy
def call(body) {
boolean PIPELINE_DEBUG = ("${env.PIPELINE_DEBUG}"!="0")
if(PIPELINE_DEBUG){ println "[DEBUG] Pipeline Debug Logging Enabled" }
   try{ 
       debugOptions { flag = PIPELINE_DEBUG }
       println DebugOptions.instance.flag
   } catch (Exception e) {
      println e.message
      error e.message
   }
}
// rest of pipeline implementation

Project Jenkinsfile

#!groovy
library "utils"
standardPipeline()

Build output

[Pipeline] echo
[DEBUG] Pipeline Debug Logging Enabled
[Pipeline] End of Pipeline 
[Bitbucket] Notifying commit build result
[Bitbucket] Build result notified
java.lang.NullPointerException
Finished: FAILURE

Questions

1. Is there a way to get more information about the nullpointer exception (like a stack trace)? I have tried to throw e.message in lieu of the error e.message and I get the same output.
2. Is there a plugin that I need to make this happen? I've got all the Pipeline plugins that I am aware of (especially Pipeline-Groovy)
3. In src/com/foo/utils/DebugOptions.groovy do I need the semicolon after the package line?
4. Can someone point out where my problem actually is?
5. Lastly, and I know it's subjective, but is there anything I should improve upon with this code? For one, I don't care for the case-sensitive-only difference in D/debugOptions.

Thank you!