handle segmentation violation

[nitesh3108]

Description

Added a nil check to skip processing pvs without ClaimRef. This will prevent karavi-metrics-powerscale from crashing when there are unbound pv s in clusters

GitHub Issues

List the GitHub issues impacted by this PR:

GitHub Issue #
dell/csm#1019

Checklist:

• I have performed a self-review of my own code to ensure there are no formatting, vetting, linting, or security issues
• I have verified that new and existing unit tests pass locally with my changes
• I have not allowed coverage numbers to degenerate
• I have maintained at least 90% code coverage
• I have inspected the Grafana dashboards to verify the data is displayed properly
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have maintained backward compatibility

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please also list any relevant details for your test configuration

• make unit test results
  
• topology test passed
  
• metrics test passed
  

[csmbot]

Can one of the admins verify this patch?

[donatwork]

Looks like the unit tests is below 90% in one package.

[shefali-malhotra]

Updated the metrics e2e and topology test cases screenshot

[rajendraindukuri]

skip e2e test

[rajendraindukuri]

e2e pass

[shefali-malhotra]

LGTM

[donatwork]

skip e2e test

[rajendraindukuri]

e2e pass

[rajendraindukuri]

skip e2e test

[donatwork]

e2e pass