ofz: detect short read

Change-Id: I1d394e914c4791a2bc3a8f3dbb1cf200e7d528fe
Reviewed-on: https://gerrit.libreoffice.org/44691Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

emfio/source/reader/wmfreader.cxx

@@ -514,7 +514,7 @@ namespace emfio
                 if ( nLength )
                 {
                     std::unique_ptr<char[]> pChar(new char[ ( nLength + 1 ) &~ 1 ]);
-                    mpInputStream->ReadBytes(pChar.get(), (nLength + 1) &~ 1);
+                    nLength = std::min<sal_uInt64>(nLength, mpInputStream->ReadBytes(pChar.get(), (nLength + 1) &~ 1));
                     OUString aText( pChar.get(), nLength, GetCharSet() );
                     pChar.reset();
                     Point aPosition( ReadYX() );