GetNextSwapTextureSetIndex incorrect code

`pIndices` might be uninitialized. Reported by @Vixea . The fix is not trivial due to the SteamVR API, so opening an issue instead.
https://github.com/alvr-org/ALVR/blob/1a4194ff137937c0a4f416ad2d6d1acedb851e8a/alvr/server_openvr/cpp/platform/win32/OvrDirectModeComponent.cpp#L145-L148

Should be replace to something like:
```C++
( *pIndices )[ i ] = ++pSet->unIndex % 3;
```