Index: branches/5.1.x/core/kernel/db/cat_dbitem.php
===================================================================
diff -u -N -r13545 -r13811
--- branches/5.1.x/core/kernel/db/cat_dbitem.php	(.../cat_dbitem.php)	(revision 13545)
+++ branches/5.1.x/core/kernel/db/cat_dbitem.php	(.../cat_dbitem.php)	(revision 13811)
@@ -1,6 +1,6 @@
 <?php
 /**
-* @version	$Id: cat_dbitem.php 13545 2010-05-11 19:19:58Z alex $
+* @version	$Id: cat_dbitem.php 13811 2010-07-07 09:41:05Z alex $
 * @package	In-Portal
 * @copyright	Copyright (C) 1997 - 2009 Intechnic. All rights reserved.
 * @license      GNU/GPL
@@ -107,10 +107,14 @@
 	function Update($id=null, $system_update=false)
 	{
 		$this->VirtualFields['ResourceId'] = Array();
-		$this->SetDBField('Modified', adodb_mktime() );
-		$this->UpdateFormattersSubFields(array('Modified'));
-		$this->SetDBField('ModifiedById', $this->Application->RecallVar('user_id'));
 
+		if ($this->GetChangedFields()) {
+			$now = adodb_mktime();
+			$this->SetDBField('Modified_date', $now);
+			$this->SetDBField('Modified_time', $now);
+			$this->SetDBField('ModifiedById', $this->Application->RecallVar('user_id'));
+		}
+
 		if ($this->useFilenames) {
 			$this->checkFilename();
 			$this->generateFilename();
Index: branches/5.1.x/core/units/categories/categories_event_handler.php
===================================================================
diff -u -N -r13581 -r13811
--- branches/5.1.x/core/units/categories/categories_event_handler.php	(.../categories_event_handler.php)	(revision 13581)
+++ branches/5.1.x/core/units/categories/categories_event_handler.php	(.../categories_event_handler.php)	(revision 13811)
@@ -1,6 +1,6 @@
 <?php
 /**
-* @version	$Id: categories_event_handler.php 13581 2010-05-19 07:33:23Z alex $
+* @version	$Id: categories_event_handler.php 13811 2010-07-07 09:41:05Z alex $
 * @package	In-Portal
 * @copyright	Copyright (C) 1997 - 2009 Intechnic. All rights reserved.
 * @license      GNU/GPL
@@ -1304,7 +1304,9 @@
 			$object =& $event->getObject();
 			/* @var $object kDBItem */
 
-			$object->SetDBField('ModifiedById', $this->Application->RecallVar('user_id'));
+			if ($object->GetChangedFields()) {
+				$object->SetDBField('ModifiedById', $this->Application->RecallVar('user_id'));
+			}
 
 			$this->_beforeItemChange($event);
 		}
@@ -1556,8 +1558,10 @@
 
 			$now = adodb_mktime();
 
-			$object->SetDBField('Modified_date', $now);
-			$object->SetDBField('Modified_time', $now);
+			if ($object->GetChangedFields()) {
+				$object->SetDBField('Modified_date', $now);
+				$object->SetDBField('Modified_time', $now);
+			}
 
 			$object->setRequired('PageCacheKey', $object->GetDBField('OverridePageCacheKey'));
 			$object->SetDBField('Template', $this->_stripTemplateExtension( $object->GetDBField('Template') ));
Index: branches/5.1.x/core/install/upgrades.sql
===================================================================
diff -u -N -r13789 -r13811
--- branches/5.1.x/core/install/upgrades.sql	(.../upgrades.sql)	(revision 13789)
+++ branches/5.1.x/core/install/upgrades.sql	(.../upgrades.sql)	(revision 13811)
@@ -1922,3 +1922,6 @@
 UPDATE ConfigurationValues
 SET DisplayOrder = DisplayOrder - 0.01
 WHERE ModuleOwner = 'In-Portal' AND `Section` = 'in-portal:configure_categories' AND DisplayOrder > 10.07;
+
+# ===== v 5.1.0 =====
+UPDATE Events SET Headers = NULL WHERE Headers = '';
Index: branches/5.1.x/core/units/helpers/email_message_helper.php
===================================================================
diff -u -N -r13276 -r13811
--- branches/5.1.x/core/units/helpers/email_message_helper.php	(.../email_message_helper.php)	(revision 13276)
+++ branches/5.1.x/core/units/helpers/email_message_helper.php	(.../email_message_helper.php)	(revision 13811)
@@ -28,7 +28,7 @@
 				}
 			}
 
-			$ret['Headers'] = implode("\n", $headers);
+			$ret['Headers'] = $headers ? implode("\n", $headers) : null; // it's null field
 
 			$lines = array_slice($lines, $line_id + 1);