…pensource#8902)

**Description**
If a path in the --file-list file contains a NUL character, cppcheck
keeps opening the same folder over and over until it crashes

**Crash Replication**
```shell
mkdir -p d/s; printf 'd\0\n' > list.txt  && /path/to/cppcheck --file-list=list.txt
```
seg fault is expected

**Proposed Patch**
If a path in --file-list file contains NUL character, reject it.

---------

Co-authored-by: chencheng mao <[email protected]>
Co-authored-by: Claude Fable 5.1 <[email protected]>

…eck-opensource#8914)

Co-authored-by: chrchr-github <[email protected]>

…check-opensource#8915)