Update 43c: Level Editor Prefab and New York (Winter) fixes

Map Changes: New York City (Winter):

• fixed aurora borealis FX having collision, blocking Heavy's helicopter

Level Editor:

• potential fix for level editor stairways resulting in weird behavior when characters used them at high speeds

• fixed prefab getting moved directly to a harddrive folder (like "C:/") if it got added to a map with an empty name (for example, after opening the level editor and then adding a prefab, and not loading/saving a map beforehand)

• fixed bugged "ghost" object that always was hidden and at 0,0,0 appearing on the level editor actor list

• fixed placed prefabs showing up as a prefab object and as an unpacked folder, even if they weren't unpacked yet

• fixed level editor objects that reset ever yround (like "Vent Door" or "AI Customer") not working correctly inside prefabs