fix openapi import nil deref

[dogancanbakir]

Proposed changes

Closes #5070

$ go run . -sf secrets.yml -im openapi -l openapi.yml

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v3.2.4

                projectdiscovery.io

[INF] Current nuclei version: v3.2.4 (latest)
[INF] Current nuclei-templates version: v9.8.1 (latest)
[WRN] Scan results upload to cloud is disabled.
[INF] New templates added in latest release: 77
[INF] Templates loaded for current scan: 24
[INF] Executing 21 signed templates from projectdiscovery/nuclei-templates
[WRN] Loading 3 unsigned templates for scan. Use with caution.
[INF] Targets loaded for current scan: 1
[INF] Using Interactsh Server: oast.site
[INF] No results found. Better luck next time!

Checklist

• Pull request is created against the dev branch
• All checks passed (lint, unit/integration/regression tests etc.) with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[tarunKoyalwar]

lgtm !

$ ./nuclei -l openapi.yaml -im openapi

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v3.2.4

		projectdiscovery.io

[INF] Current nuclei version: v3.2.4 (latest)
[INF] Current nuclei-templates version: v9.8.5 (latest)
[WRN] Scan results upload to cloud is disabled.
[INF] New templates added in latest release: 142
[INF] Templates loaded for current scan: 21
[INF] Executing 21 signed templates from projectdiscovery/nuclei-templates
[INF] Targets loaded for current scan: 1
[INF] No results found. Better luck next time!