Wrong plugin_header_nonexistent_requires_wp for 6.3

[kkmuffme]

0 0 ERROR plugin_header_nonexistent_requires_wp Requires at least: 6.3. The "Requires at least" value in your plugin header is not valid. This version of WordPress does not exist (yet). https://developer.wordpress.org/plugins/plugin-basics/header-requirements/#header-fields

Really?

[kkmuffme]

Ah, this is bc of #976 - if the API does not return a version, then it just assumes there are no versions at all.

Instead it should use the current global $wp_version value as "max value" at least (didn't check the code, but assuming this doesn't actually validate versions at all and just version_compare <= ?) - otherwise not report this error at all, if it fails to get the WP versions

[kkmuffme]

Same for nonexistent_tested_upto_header