Don't try to parse if no targets

[attiasas]

• The pull request is targeting the dev branch.
• The code has been validated to compile successfully by running go vet ./....
• The code has been formatted properly using go fmt ./....
• All static analysis checks passed.
• All tests have passed. If this feature is not already covered by the tests, new tests have been added.
• Updated the Contributing page / ReadMe page / CI Workflow files if needed.
• All changes are detailed at the description. if not already covered at JFrog Documentation, new documentation have been added.

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In jf scan, it is possible to pass arguments with no actual artifacts to scan.
That caused the following issue:

[Error] failed to record results: ParseNewTargetResults must be called before starting to parse issues

[github-actions]

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🐸 JFrog Frogbot

[eranturgeman]

add a tests case if some test for this exists