Uninitialized string offset: 35 on line 725 tcpdi_parser.php

[Manitnelav]

I get this error Uninitialized string offset: 35 application/third_party/tcpdf/tcpdi_parser.php 725

The line on 725 is in method getRawObject

while (strspn($data[$offset], "\x00\x09\x0a\x0c\x0d\x20") == 1) {
    $offset++;
}

Some idea how to change it? I don't understand what getRawObject should return in this cases.