ENGCOM-3422: Add availability to leave empty config for events.xml #19146

Author: sivaschenko

lib/internal/Magento/Framework/Event/Test/Unit/Config/_files/invalidEventsXmlArray.php

@@ -4,10 +4,6 @@
  * See COPYING.txt for license details.
  */
 return [
-    'without_event_handle' => [
-        '<?xml version="1.0"?><config></config>',
-        ["Element 'config': Missing child element(s). Expected is ( event ).\nLine: 1\n"],
-    ],
     'event_without_required_name_attribute' => [
         '<?xml version="1.0"?><config><event name="some_name"></event></config>',
         ["Element 'event': Missing child element(s). Expected is ( observer ).\nLine: 1\n"],

lib/internal/Magento/Framework/Event/etc/events.xsd

@@ -9,7 +9,7 @@
     <xs:element name="config">
         <xs:complexType>
             <xs:sequence>
-                <xs:element name="event" type="eventDeclaration" minOccurs="1" maxOccurs="unbounded">
+                <xs:element name="event" type="eventDeclaration" minOccurs="0" maxOccurs="unbounded">
                     <xs:unique name="uniqueObserverName">
                         <xs:annotation>
                             <xs:documentation>