Inconsistent error message for delete command when format is right

[nus-se-script]

Since delete contact 1 follows the correct format, the app should not output the message of invalid format. Instead, it should warn that the index is not valid.

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_{[original: nus-cs2103-AY2324S1/pe-interim#5985] [original labels: severity.Low type.FeatureFlaw]}

[Nixx162]

Team's Response

As given in our UG, CONTACT_ID needs to be a positive integer. Since 0 is not a positive integer, this is indeed not the correct format.

Duplicate status (if any):

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