check for empty charset

dialect.go

@@ -146,11 +146,13 @@ func (b *Base) CreateTableSql(table *Table, tableName, storeEngine, charset stri
 		sql += " ENGINE=" + storeEngine
 	}
 	if b.dialect.SupportCharset() {
-		if charset == "" {
+		if len(charset) == 0 {
 			charset = b.dialect.URI().Charset
 		}
+		if len(charset) > 0 {
 			sql += " DEFAULT CHARSET " + charset
 		}
+	}
 	sql += ";"
 	return sql
 }