Coding Standards: Explicitly return false in magic __isset() methods.

This commit fixes an issue where some magic `__isset()` methods were potentially returning `void` (if the prop is not in an allow-listed array of fields) instead of an explicit boolean `false`.

Addressed methods:
* `WP_Comment::__isset()`
* `WP_Query::__isset()`

Follow-up to [28523], [31151], [34583], [34599].

Props justlevine.
See #52217.

git-svn-id: https://develop.svn.wordpress.org/trunk@59337 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/class-wp-comment.php

@@ -351,14 +351,16 @@ public function populated_children( $set ) {
 	 *
 	 * @since 4.4.0
 	 *
-	 * @param string $name Property name.
-	 * @return bool
+	 * @param string $name Property to check if set.
+	 * @return bool Whether the property is set.
 	 */
 	public function __isset( $name ) {
 		if ( in_array( $name, $this->post_fields, true ) && 0 !== (int) $this->comment_post_ID ) {
 			$post = get_post( $this->comment_post_ID );
 			return property_exists( $post, $name );
 		}
+
+		return false;
 	}
 
 	/**

src/wp-includes/class-wp-query.php

@@ -4011,6 +4011,8 @@ public function __isset( $name ) {
 		if ( in_array( $name, $this->compat_fields, true ) ) {
 			return isset( $this->$name );
 		}
+
+		return false;
 	}
 
 	/**