Users: Remove unnecessary `is_null()` call in `get_avatar_data()`.

The `! is_null()` portion of the condition is unnecessary, because `isset()` checks whether a variable is set *and* is not null.

Props JPry.
Fixes #44927.
Built from https://develop.svn.wordpress.org/trunk@44351


git-svn-id: http://core.svn.wordpress.org/trunk@44181 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/link-template.php

@@ -4052,7 +4052,7 @@ function get_avatar_data( $id_or_email, $args = null ) {
 	 */
 	$args = apply_filters( 'pre_get_avatar_data', $args, $id_or_email );
 
-	if ( isset( $args['url'] ) && ! is_null( $args['url'] ) ) {
+	if ( isset( $args['url'] ) ) {
 		/** This filter is documented in wp-includes/link-template.php */
 		return apply_filters( 'get_avatar_data', $args, $id_or_email );
 	}

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44350';
+$wp_version = '5.1-alpha-44351';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.