Fix empty string encoding mappings to NULL
Fix empty string encoding mappings to NULL

sodabrew/mysql2,kamipo/mysql2,brianmario/mysql2,jeremy/mysql2,jeremy/mysql2,kamipo/mysql2,jeremy/mysql2,sodabrew/mysql2,brianmario/mysql2,kamipo/mysql2,brianmario/mysql2,kamipo/mysql2,sodabrew/mysql2