Fix overlay not working after alt-tabbing / playing steamworks

[l1m0n3]

Tested on DirectX12 enabled + fullscreen.

When alt-tabbing, d3d12_deinitialize_imgui which is called by d3d_resize_buffers_hook gets called.
In d3d12_deinitialize_imgui, it nullifies m_d3d12_command_queue and it always be nullptr after that.
In Present hook, it checks if command queue is valid and also steamworks is not active.
If checks failed, it will return early but never assign back to m_is_inside_present = false.
This will cause an issue as title says.

This PR fixes the issue by just keeping command queue when deinitializing and assigning the flag back properly.

I know nothing about DirectX or rendering stuff, so sorry if this is not a proper fix.

[Fexty12573]

Thank you for the PR! Looks good, I will merge it once the builds complete