Issue #2491033 by daffie, mgifford, dawehner: Return value of Database::getLog() is inconsistent -- always return an array, even when empty

core/lib/Drupal/Core/Database/Database.php

@@ -129,7 +129,7 @@ abstract class Database {
    */
   final public static function getLog($logging_key, $key = 'default') {
     if (empty(self::$logs[$key])) {
-      return NULL;
+      return [];
     }
     $queries = self::$logs[$key]->get($logging_key);
     self::$logs[$key]->end($logging_key);

core/tests/Drupal/KernelTests/Core/Database/LoggingTest.php

@@ -126,4 +126,13 @@ class LoggingTest extends DatabaseTestBase {
     $this->assertEqual(count($queries2), 1, 'Correct number of queries recorded for second connection.');
   }
 
+  /**
+   * Tests that getLog with a wrong key return an empty array.
+   */
+  function testGetLoggingWrongKey() {
+    $result = Database::getLog('wrong');
+
+    $this->assertEqual($result, [], 'The function getLog with a wrong key returns an empty array.');
+  }
+
 }