Fix URL generation bug in postman collection exporter #2496

[gtlsgamr]

Description

This PR fixes an issue mentioned in #2496 where exporting a postman collection which has variables in the url leads to getting only '/' in the place of full URL. Now we have a check for template variables before generating URL hostname so that it does not try to create a URL variable anymore which led to the mentioned error.

BEFORE
Bruno -

Postman -

AFTER
Postman -

Contribution Checklist:

• [x ] The pull request only addresses one issue or adds one feature.
• [x ] The pull request does not introduce any breaking changes
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