Upstream error handling fix, seems worth merging

[orospakr]

I just took a quick peek at what divergence there is between your fork and upstream svn, and I noticed this patch:

git-svn-id: https://quazip.svn.sourceforge.net/svnroot/quazip/trunk@133 bf82bb6f-4128-0410-aed8-a7a134390cb4

@@ -440,7 +440,10 @@ qint64 QuaZipFile::readData(char *data, qint64 maxSize)
{
p->setZipError(UNZ_OK);
qint64 bytesRead=unzReadCurrentFile(p->zip->getUnzFile(), data, (unsigned)maxSize);

• if(bytesRead<0) p->setZipError((int)bytesRead);
• if (bytesRead < 0) {
• p->setZipError((int) bytesRead);
• return -1;
• }
  return bytesRead;
  }