feat(fastify): Do not crash if enableVersioning is not used

[Fcmam5]

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

Issue Number: #13496

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 9ab9e29c-a6c7-418a-943d-6f81a0507a00

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.124%

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Totals
Change from base Build e56f6d99-d9bc-426a-b9ef-ed11406d7e1c:	0.0%
Covered Lines:	6737
Relevant Lines:	7313

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💛 - Coveralls

[micalevisk]

I guess we'd have to change the versioningOptions field definition to mark it as optional

[Fcmam5]

@micalevisk I agree, I just pushed now. Please check again

[kamilmysliwiec]

LGTM