General: Introduce WP_Error::has_errors() method and use it where appropriate.

Props robdxw, DrewAPicture, SergeyBiryukov.
Fixes #42742.

git-svn-id: https://develop.svn.wordpress.org/trunk@42761 602fd350-edb4-49c9-b593-d223f7449a82

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

@@ -71,7 +71,7 @@ class WP_Error {
 	 * @return array List of error codes, if available.
 	 */
 	public function get_error_codes() {
-		if ( empty( $this->errors ) ) {
+		if ( ! $this->has_errors() ) {
 			return array();
 		}
 
@@ -161,6 +161,20 @@ class WP_Error {
 		}
 	}
 
+	/**
+	 * Verify if the instance contains errors.
+	 *
+	 * @since 5.0.0
+	 *
+	 * @return bool
+	 */
+	public function has_errors() {
+		if ( ! empty( $this->errors ) ) {
+			return true;
+		}
+		return false;
+	}
+
 	/**
 	 * Add an error or append additional message to an existing error.
 	 *