If the user calls QLocalSocket::setReadBufferSize() with a value less
than the current size of the pipe buffer, startAsyncRead() would call
ReadFileEx() with invalid parameters:
ReadFileEx(handle, nullptr, some_big_value, ...);
Change-Id: I3d153e3ec34f8038dc001c1c896aeceb666a8979
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>