The current WebVTT parser incorrectly interprets the region id setting string `'id: foo'` as a region with an id of `''`. However, this behavior deviates from the specification. According to the spec, the parser should initially split the input string based on spaces. If the first `':'` in a setting string is either the first or last character of that string, it should proceed to the next string. In the case of `'id: foo'`, it should be parsed as `'id:'` and `'foo'`, both of which are considered invalid id strings.

WPT: https://wpt.fyi/results/webvtt/parsing/file-parsing/tests/regions-id.html?label=experimental&label=master&aligned