Not helpful error message for delete history for patient

[tau-bar]

Expected:

• Expected Behaviour: Error to tell me that the index is out of range.

Actual:

• Actual Behaviour: Error that states the index cannot be empty.

• Why that severity? It causes a minor inconvenience for users who might take a while to figure out what the actual problem is.

Steps to reproduce:

1. Try to delete a medical history that is out of range. eg. pt md 1289371289391 i/9

Screenshots:

[nus-pe-bot]

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