Add nullptr check in logCertVerificationFailure

[thisisnsh]

Describe your changes

• In logCertVerificationFailure check if following pointers are not null before accessing them:
  • X509_STORE_CTX cert context
  • X509 cert
  • X509_NAME subject name
• Add tests
• Add error code, message and depth to log for better debugging

Testing performed

• Unit tests