Enable all map filters in ClearSky mode

[cropinghigh]

Seems like Clear Sky doesn't have map filter functionality, thus all CUITaskWnd::Is... functions always return false, resulting in unusable task focus and hide/show buttons.
Additional testing requested.
Should not affect Call of Pripyat mode.

[cropinghigh]

Also fixes always invisible treasure icons

[Xottab-DUTY]

Thanks for helping to find the culprit!
I remember that everything was working, so I didn't knew the clue when #1835 was reported.
It turned out that I forgot that filters should be always enabled by default when I was working on dbc8a5c, so I made them disabled in that commit accidentally.

The correct fix is to make the functions to return true if the filters are missing, no need to specifically check for Clear Sky mode.
And you also need to change CUIMapFilters::IsFilterEnabled in xrGame/UIMapFilters.cpp so it looks like this:

bool CUIMapFilters::IsFilterEnabled(eSpotsFilter filter) const
{
    return !m_filters[filter] || m_filters[filter]->GetCheck();
}

Could you make this change?
Oh nevermind, it's fast to do through the GitHub interface. I did that.