sip.instance wasnt written/loaded to/from the database; thanks to Andreas Granig

scripts/ser_mysql.sh

@@ -333,7 +333,7 @@ CREATE TABLE aliases (
   state tinyint(1) unsigned NOT NULL default '0',
   flags int(11) NOT NULL default '0',
   user_agent varchar(50) NOT NULL default '',
-  instance varchar(80) NOT NULL default '',
+  instance varchar(80) default NULL,
   PRIMARY KEY($USERCOL, domain, contact),
   INDEX aliases_contact (contact)
 ) $TABLE_TYPE;
@@ -391,7 +391,7 @@ CREATE TABLE location (
   state tinyint(1) unsigned NOT NULL default '0',
   flags int(11) NOT NULL default '0',
   user_agent varchar(50) NOT NULL default '',
-  instance varchar(80) NOT NULL default '',
+  instance varchar(80) default NULL,
   PRIMARY KEY($USERCOL, domain, contact)
 ) $TABLE_TYPE;