Formatting: Loosen the type checking in `_sanitize_text_fields()`.

[44618] added strict type checking to `_sanitize_text_fields()`, which has caused some compat issues with plugins.

We can loosen the type checking to only reject objects and arrays, and cast other types to string.

Props Nick_theGeek, pento.
Fixes #41450.


Built from https://develop.svn.wordpress.org/trunk@44731


git-svn-id: http://core.svn.wordpress.org/trunk@44562 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/formatting.php

@@ -5153,10 +5153,12 @@ function sanitize_textarea_field( $str ) {
  * @return string Sanitized string.
  */
 function _sanitize_text_fields( $str, $keep_newlines = false ) {
-	if ( ! is_string( $str ) ) {
+	if ( is_object( $str ) || is_array( $str ) ) {
 		return '';
 	}
 
+	$str = (string) $str;
+
 	$filtered = wp_check_invalid_utf8( $str );
 
 	if ( strpos( $filtered, '<' ) !== false ) {

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-beta3-44730';
+$wp_version = '5.1-beta3-44731';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.