fix: Check nil pointer in buildPaths()

[MonicaisHer]

This PR will resolve #494

If your build fails due to your commit message not passing the build checks, please review the guidelines here: https://github.com/edgexfoundry/go-mod-bootstrap/blob/main/.github/Contributing.md

PR Checklist

Please check if your PR fulfills the following requirements:

• I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• I am not introducing a new dependency (add notes below if you are)
• I have added unit tests for the new feature or bug fix (if not, why?)
• I have fully tested (add details below) this the new feature or bug fix (if not, why?)
• I have opened a PR for the related docs change (if not, why?)

Testing Instructions

Build and install edegfxoundry using go mod bootstrapper from this PR

snapcraft
snap install ./edgexfoundry_3.0.0-dev.114_amd64.snap --dangerous

Set env variables:

sudo snap set edgexfoundry apps.core-data.config.edgex-config-provider='none'
sudo snap set edgexfoundry apps.core-data.config.edgex-common-config=./config/core-common-config-bootstrapper/res/configuration.yaml
sudo snap restart edgexfoundry.core-data

Check logs:

$ journalctl -f | grep core-data
Mär 28 10:05:43 ubuntu edgexfoundry.core-data[271774]: level=INFO ts=2023-03-28T08:05:43.543578388Z app=core-data source=config.go:192 msg="Common configuration loaded from file with 0 overrides applied"
...
Mär 28 10:05:43 ubuntu edgexfoundry.core-data[271774]: level=INFO ts=2023-03-28T08:05:43.572789735Z app=core-data source=httpserver.go:133 msg="Web server starting (localhost:59880)"
Mär 28 10:05:43 ubuntu edgexfoundry.core-data[271774]: level=INFO ts=2023-03-28T08:05:43.572801546Z app=core-data source=message.go:50 msg="Service dependencies resolved..."
Mär 28 10:05:43 ubuntu edgexfoundry.core-data[271774]: level=INFO ts=2023-03-28T08:05:43.572805912Z app=core-data source=message.go:51 msg="Starting core-data 3.0.0-dev.114 "
Mär 28 10:05:43 ubuntu edgexfoundry.core-data[271774]: level=INFO ts=2023-03-28T08:05:43.572809113Z app=core-data source=message.go:55 msg="This is the Core Data Microservice"
Mär 28 10:05:43 ubuntu edgexfoundry.core-data[271774]: level=INFO ts=2023-03-28T08:05:43.572812418Z app=core-data source=message.go:58 msg="Service started in: 33.37508ms

New Dependency Instructions (If applicable)

[codecov-commenter]

Codecov Report

Merging #495 (e614a65) into main (e43ae9c) will not change coverage.
The diff coverage is 100.00%.

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@@           Coverage Diff           @@
##             main     #495   +/-   ##
=======================================
  Coverage   58.54%   58.54%           
=======================================
  Files          27       27           
  Lines        2118     2118           
=======================================
  Hits         1240     1240           
  Misses        803      803           
  Partials       75       75           

Impacted Files	Coverage Δ
bootstrap/environment/variables.go	90.14% <100.00%> (ø)

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[lenny-goodell]

LGTM