fix ttrss_feeds.last_update defaulting to 0 on mysql, set to null instead

bump schema

schema/ttrss_schema_mysql.sql

@@ -101,7 +101,7 @@ create table ttrss_feeds (id integer not null auto_increment primary key,
 	icon_url varchar(250) not null default '',
 	update_interval integer not null default 0,
 	purge_interval integer not null default 0,
-	last_updated datetime default 0,
+	last_updated datetime default null,
 	last_error varchar(250) not null default '',
 	favicon_avg_color varchar(11) default null,
 	site_url varchar(250) not null default '',
@@ -281,7 +281,7 @@ create table ttrss_tags (id integer primary key auto_increment,
 
 create table ttrss_version (schema_version int not null) ENGINE=InnoDB DEFAULT CHARSET=UTF8;
 
-insert into ttrss_version values (129);
+insert into ttrss_version values (130);
 
 create table ttrss_enclosures (id integer primary key auto_increment,
 	content_url text not null,

schema/ttrss_schema_pgsql.sql

@@ -263,7 +263,7 @@ create index ttrss_tags_post_int_id_idx on ttrss_tags(post_int_id);
 
 create table ttrss_version (schema_version int not null);
 
-insert into ttrss_version values (129);
+insert into ttrss_version values (130);
 
 create table ttrss_enclosures (id serial not null primary key,
 	content_url text not null,

schema/versions/mysql/130.sql

@@ -0,0 +1,7 @@
+BEGIN;
+
+alter table ttrss_feeds alter column last_updated set default null;
+
+UPDATE ttrss_version SET schema_version = 130;
+
+COMMIT;

schema/versions/pgsql/130.sql

@@ -0,0 +1,5 @@
+BEGIN;
+
+UPDATE ttrss_version SET schema_version = 130;
+
+COMMIT;