Fix undefined variable bug

[kazuhitoyokoi]

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Proposed changes

The node generated by Swagger template throws an error when the node refers to the undefined variables. To fix the problem, I added conditions to check the values.

Checklist

• I have read the contribution guidelines
• For non-bugfix PRs, I have discussed this change on the mailing list/slack team.
• I have run grunt to verify the unit tests pass
• I have added suitable unit tests to cover the new/changed functionality

[kazuhitoyokoi]

@HiroyasuNishiyama Thank you!

[coveralls]

Coverage remained the same at 73.487% when pulling 73e736e on kazuhitoyokoi:master into 321f760 on node-red:master.

[coveralls]

Coverage remained the same at 73.487% when pulling 73e736e on kazuhitoyokoi:master into 321f760 on node-red:master.