Minor db schema corrections

db_schema.sql

@@ -47,7 +47,7 @@ CREATE TABLE IF NOT EXISTS `courses_data` (
   `deleted` INTEGER NOT NULL DEFAULT '0',
   `title` text NOT NULL DEFAULT '',
   `short` varchar(32) NOT NULL DEFAULT '',
-  `handle` varchar(32) NOT NULL DEFAULT '',
+  `handle` varchar(32) NOT NULL,
   `organizer` text NOT NULL DEFAULT '',
   `subject` varchar(32) NOT NULL DEFAULT '',
   `credits` INTEGER NOT NULL DEFAULT '0',
@@ -260,8 +260,8 @@ CREATE TABLE IF NOT EXISTS `announcements` (
 	`level` INTEGER NOT NULL DEFAULT 0,
 	`visible` INTEGER NOT NULL DEFAULT 0,
 	`deleted` INTEGER NOT NULL DEFAULT 0,
-  `time_publish` datetime DEFAULT '',
-  `time_expire` datetime DEFAULT '',
+  `time_publish` datetime,
+  `time_expire` datetime,
   `time_created` datetime NOT NULL,
   `time_updated` datetime NOT NULL,
   `created_by` INTEGER NOT NULL
@@ -271,7 +271,7 @@ CREATE TABLE IF NOT EXISTS `featured` (
 	`title` text NOT NULL DEFAULT '',
 	`text` text NOT NULL DEFAULT '',
 	`internal` text NOT NULL DEFAULT '',
-	`type` varchar(32) NOT NULL DEFAULT '',
+	`type` varchar(32) NOT NULL,
 	`param` text NOT NULL DEFAULT '',
 	`param2` text NOT NULL DEFAULT '',
 	`order` INTEGER DEFAULT NULL,