Remove useless return in ZipCryptoReaderValid::read()

src/zipcrypto.rs

@@ -118,10 +118,6 @@ impl<R: std::io::Read> std::io::Read for ZipCryptoReaderValid<R>
 {
     fn read(&mut self, mut buf: &mut [u8]) -> std::io::Result<usize>
     {   
-        if buf.len() == 0 {
-            return Ok(0);
-        }
-        
         //Note: There might be potential for optimization. Inspiration can be found at:
         //https://github.com/kornelski/7z/blob/master/CPP/7zip/Crypto/ZipCrypto.cpp