Update index.py

[booskz]

This PR fixes a critical IndexError: list index out of range that occurs when using Certbot to generate certificates for root domains (e.g., example.com).
Problem

In the get_domain_rr() function, the code splits the domain into tokens and removes the last two elements (the TLD and the main domain).

For a subdomain like www.opty.fun, tokens ['www', 'opty', 'fun'] becomes ['www'] after del tokens[-2:].

For a root domain like opty.fun, tokens ['opty', 'fun'] becomes an empty list [].

The original code then attempts to access tokens[0] to check for wildcard symbols without verifying if the list is empty, leading to a runtime crash.
Solution

Added a conditional check if tokens: before accessing tokens[0]. This ensures that if the list is empty (indicating a root domain), it skips the wildcard check and directly inserts the _acme-challenge prefix.
Verification Results

I have tested this fix in an Alibaba Cloud Function Compute (FC) environment: | Domain Input | DEVS_DOMAIN | Resulting RR | Status | | :--- | :--- | :--- | :--- | | Root Domain | opty.fun | _acme-challenge | Fixed | | Subdomain | www.opty.fun | _acme-challenge.www | Works | | Wildcard | *.opty.fun | _acme-challenge | Works |