Cache API: Address code quality issues with wp_cache_switch_to_blog().

This addresses 3 PHPStan errors at rule level 8:

* `arguments.count`: Function `wp_cache_switch_to_blog_fallback()` invoked with 1 parameter, 0 required.
* `method.nonObject`: Cannot call method `switch_to_blog()` on `class-string|object`.                                                             
* `missingType.return`: Function `wp_cache_switch_to_blog()` has no return type specified.                                                                                                                                         

Developed as subset of WordPress/wordpress-develop#11151

Follow-up to r61760.

Props westonruter, johnjamesjacoby.
See #23290, #64238.

Built from https://develop.svn.wordpress.org/trunk@62028


git-svn-id: http://core.svn.wordpress.org/trunk@61310 1a063a9b-81f0-0310-95a4-ce76da25c4cd

Author: westonruter

wp-includes/cache-compat.php

@@ -327,11 +327,11 @@ function wp_cache_set_multiple_salted( $data, $group, $salt, $expire = 0 ) {
 	 *
 	 * @param int $blog_id Site ID.
 	 */
-	function wp_cache_switch_to_blog( $blog_id ) {
+	function wp_cache_switch_to_blog( $blog_id ): void {
 		global $wp_object_cache;
 
 		// Attempt to use the drop-in object cache method if it exists.
-		if ( method_exists( $wp_object_cache, 'switch_to_blog' ) ) {
+		if ( is_object( $wp_object_cache ) && method_exists( $wp_object_cache, 'switch_to_blog' ) ) {
 			$wp_object_cache->switch_to_blog( $blog_id );
 			return;
 		}
@@ -340,6 +340,6 @@ function wp_cache_switch_to_blog( $blog_id ) {
 		 * Perform a fallback blog switch, which will reinitialize the caches
 		 * for the new blog ID.
 		 */
-		wp_cache_switch_to_blog_fallback( $blog_id );
+		wp_cache_switch_to_blog_fallback();
 	}
 endif;

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '7.0-beta5-62027';
+$wp_version = '7.0-beta5-62028';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.