search_api 8.x-1.0-rc4

This is the fourth release candidate for the Search API module's 8.x-1.0 version.

Compared to the RC 3 release, this release only contains a single bug fix, for a major bug introduced in the RC 3 release: #2869121-40: Do not set an error message when "Fulltext search" filter fails its "Required" validation.
If you had an exposed fulltext filter in a Views exposed form block and set it to "Required", it would lead to a fatal error on all pages displaying the block.

With this fixed, this release is supposed to be ready for release and contains no known (major) bugs. Unless such a bug is discovered before then, the first stable release, Search API 8.x-1.0, will be released in the middle of next week, around April 26.