[compiler] Improved OTP validation message and prompt handling

[inject3r]

Summary

Improved the OTP validation logic by making the error message more descriptive and ensuring that the prompt.done() method is only called after receiving a valid input.

How did you test this change?

• Tested the OTP input functionality by running the code and verifying that the error message is now more clear when no input is provided.
• Ensured that the prompt correctly closes after a valid OTP input and asks again if the input is invalid.
• No additional tests were required as this change only affects the user input validation logic.

[Hardanish-Singh]

LGTM!