Replace does not work for serialized data if the string does not end with a new line

To reproduce:

```
php -r 'echo serialize("aaaaabbbbbbbbbbaaaaa");' > test.txt
cat test.txt | ./go-search-replace bbbbbbbbbb ccccc
```

Expected result:
```
s:15:"aaaaacccccaaaaa";
```

Actual result: empty output

Reproduce the issue with the shown `php -r` command and pipe its output into `./go-search-replace`. Compare behavior when the serialized input lacks a trailing newline, then inspect the command's input-processing path. Done means the command emits `s:15:"aaaaacccccaaaaa";` instead of empty output for the reported input.

Written by the indexing model from the issue text.