Fix IsNailedToWorldHierarchy + prop_playergib errors.

gamemodes/zombiesurvival/entities/entities/prop_playergib/init.lua

@@ -3,10 +3,12 @@ AddCSLuaFile("shared.lua")
 
 include("shared.lua")
 
+ENT.DieTime = 0
+
 function ENT:Initialize()
 	self.m_Health = 25
 
-	if not self.DieTime then
+	if self.DieTime == 0 then
 		self.DieTime = CurTime() + GAMEMODE.GibLifeTime
 	end
 

gamemodes/zombiesurvival/gamemode/init.lua

@@ -1737,7 +1737,9 @@ end
 function GM:EvaluatePropFreeze(ent, neighbors)
 	if not ent then
 		for _, e in pairs(ents.GetAll()) do
-			self:EvaluatePropFreeze(e)
+			if e:IsValid() then
+				self:EvaluatePropFreeze(e)
+			end
 		end
 
 		return