Cast $blog_id to int in wp_cache_clear_cache() (#1054)

Third-party callers sometimes pass a non-integer (e.g. wp_cache_clear_cache('all', false)). The value flows to get_supercache_dir() -> get_blog_option(), a multisite-only function, fataling on single-site installs. Casting to int normalizes 'all'/false to 0, taking the single-site clearing path.

Fixes #1019.

Author: donnchawp

wp-cache-phase2.php

@@ -3089,6 +3089,10 @@ function wp_cache_clear_cache_on_menu() {
 function wp_cache_clear_cache( $blog_id = 0 ) {
 	global $cache_path;
 
+	// Normalize non-integer callers (e.g. 'all', false) to 0 so they take the
+	// single-site path instead of reaching get_blog_option() via the blog branch.
+	$blog_id = (int) $blog_id;
+
 	if ( $blog_id == 0 ) {
 		wp_cache_debug( 'Clearing all cached files in wp_cache_clear_cache()', 4 );
 		prune_super_cache( $cache_path . 'supercache/', true );