RawDataParser->getXrefData not fully covered by tests

I had an Exception throw by RawDataParser->getXrefData, I didn't debug this case yet, but I noticed that there's an elseif not covered by tests...
I left a var_dump inside the elseif and I ran phpunit and this var_dump didn't show on terminal (I left a var_dump outside this elseif after just to be sure that would be shown on terminal)

This elseif is not covered (RawDataParser.php:822)

 elseif ($startxrefPreg) {
            // startxref found
            $startxref = $matches[1][0];
        }

PS: I will try to debug it later, I am just opening an issue for the record

Start with RawDataParser.php around line 822 and inspect the existing PHPUnit coverage for RawDataParser->getXrefData. Reproduce the reported exception and determine the input that reaches the uncovered elseif. Done means the case has a regression test and the relevant PHPUnit tests pass.