Convert three variable assignments to the usage of combined operators

[elfring]

:eyes: Some source code analysis tools can help to find opportunities for improving software components. :thought_balloon: I propose to increase the usage of combined operators accordingly.

diff --git a/modules/datastore/src/Controller/AbstractQueryController.php b/modules/datastore/src/Controller/AbstractQueryController.php
index 813d0f25..941081ea 100644
--- a/modules/datastore/src/Controller/AbstractQueryController.php
+++ b/modules/datastore/src/Controller/AbstractQueryController.php
@@ -287,7 +287,7 @@ abstract class AbstractQueryController implements ContainerInjectionInterface {
    *   Normalized and type-casted JSON string.
    */
   public static function getPayloadJson(Request $request, $schema = NULL) {
-    $schema = $schema ?? file_get_contents(__DIR__ . "/../../docs/query.json");
+    $schema ??= file_get_contents(__DIR__ . "/../../docs/query.json");
     $payloadJson = static::getJson($request);
     $payloadJson = static::fixTypes($payloadJson, $schema);
     return $payloadJson;
diff --git a/modules/json_form_widget/src/Element/DateRange.php b/modules/json_form_widget/src/Element/DateRange.php
index 38d74c5f..16ea542b 100644
--- a/modules/json_form_widget/src/Element/DateRange.php
+++ b/modules/json_form_widget/src/Element/DateRange.php
@@ -136,7 +136,7 @@ class DateRange extends Datetime {
   public static function getFormattedTime($time) {
     $formatted = !empty($time) ? $time : '00:00:00';
     if (strlen($formatted) == 5) {
-      $formatted = $formatted . ':00';
+      $formatted .= ':00';
     }
     return $formatted;
   }
diff --git a/modules/metastore/modules/metastore_search/src/QueryBuilderTrait.php b/modules/metastore/modules/metastore_search/src/QueryBuilderTrait.php
index b342f36e..80975a2b 100644
--- a/modules/metastore/modules/metastore_search/src/QueryBuilderTrait.php
+++ b/modules/metastore/modules/metastore_search/src/QueryBuilderTrait.php
@@ -204,7 +204,7 @@ trait QueryBuilderTrait {
       'page' => 1,
       'page-size' => 10,
     ];
-    $params = $params + $defaults;
+    $params += $defaults;
 
     $end = ($params['page'] * $params['page-size']);
     $start = $end - $params['page-size'];