Core/MemoryStream: Fix assertion trigger when writing zero-sized block

src/Nazara/Core/MemoryStream.cpp

@@ -129,6 +129,8 @@ namespace Nz
 	*/
 
 	std::size_t MemoryStream::WriteBlock(const void* buffer, std::size_t size)
+	{
+		if (size > 0)
 		{
 			std::size_t endPos = static_cast<std::size_t>(m_pos + size);
 			if (endPos > m_buffer->GetSize())
@@ -139,6 +141,8 @@ namespace Nz
 			std::memcpy(m_buffer->GetBuffer() + m_pos, buffer, size);
 
 			m_pos = endPos;
+		}
+
 		return size;
 	}
 }