unzip: Unify EOF handling

[stoeckmann]

If EOF is encountered while reading the new filename after choosing 'r', avoid out of boundary access and usage of undefined memory content by treating it the same way as if the question itself was not answered.

[stoeckmann]

Proof of Concept:

1. Create a file

touch file.txt

2. Create an archive containing this file

bsdtar -acf archive.zip file.txt

3. Extract archive and only answer r without giving a new name

echo r | bsdunzip archive.zip

You can see output like

Archive:  archive.zip
replace file.txt? [y]es, [n]o, [A]ll, [N]one, [r]ename: New name:  extracting: ӯV

The actual file name is pretty random, depending on the underlying system.