fix db default charset error

* fix db default charset error

* add table charset empty check

dialect_mysql.go

@@ -568,9 +568,12 @@ func (db *mysql) CreateTableSql(table *core.Table, tableName, storeEngine, chars
 
 	if len(charset) == 0 {
 		charset = db.URI().Charset
-	} else if len(charset) > 0 {
+	} 
+	if len(charset) != 0 {
 		sql += " DEFAULT CHARSET " + charset
 	}
+	
+	
 
 	if db.rowFormat != "" {
 		sql += " ROW_FORMAT=" + db.rowFormat