Do not apply IDNA conversion to RegEx domains

[yubiuser]

What does this PR aim to accomplish?:

Fixes #2335.

When adding domains to the database we do a convertUnicodeToIDNA before. However, this is not needed for RegEx and can instead lead to side effects seen in the linked issue. This PR moves the conversion into the already existing if clause that only triggers if no RegEx is added.

P.S. The used PHP function idn_to_ascii does not convert "invalid" domains but instead returns false which will add an empty domain to the database

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[yubiuser]

Confirmed working in the linked issue report.

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/regex-block-slipping-through-the-cracks-youtube/57601/8

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/domain-address-is-not-allowed-on-blacklist/57859/2

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/pi-hole-ftl-v5-18-web-v5-15-and-core-v5-12-1-released/57894/1

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/blocking-all-tlds-of-a-domain/58025/2