zlib can return LZMA_BUF_ERROR, which indicates that either
the input or output buffer has size zero. This case should cause
the correct error to be passed back from g_converter_convert
to expand the relevant buffer. Since this error is ambiguous
as to which buffer is too small, an explicit check on the
output buffer size is added as well.
https://bugzilla.gnome.org/show_bug.cgi?id=756260
Simon McVittie
John Hiesey
Giuseppe Scrivano
Colin Walters