REST API: Correctly infer empty objects passed via query parameters.

Permit passing an empty object as the string "?obj=". The type of the passed empty argument is inferred from the registered schema.

Props TimothyBlynJacobs, steffanhalv, schlessera, dd32.
Fixes #42961.

Built from https://develop.svn.wordpress.org/trunk@47362


git-svn-id: http://core.svn.wordpress.org/trunk@47149 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/rest-api.php

@@ -1250,6 +1250,10 @@ function rest_validate_value_from_schema( $value, $args, $param = '' ) {
 	}
 
 	if ( 'object' === $args['type'] ) {
+		if ( '' === $value ) {
+			$value = array();
+		}
+
 		if ( $value instanceof stdClass ) {
 			$value = (array) $value;
 		}

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.4-beta2-47361';
+$wp_version = '5.4-beta2-47362';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.