Limiting maximum allocation size for QDataStream

When reading a QByteArray from QDataStream, the data stream first reads 4 bytes indicating the byte array payload size. It then attempts to allocate memory with the given size. In the case of reading from corrupted data, it may throw a std::bad_alloc exception due to an invalid size being read. It is better to limit the maximum allocation size and discard the allocations greater than defined maximum.