Tentative fix for nil _links table, new tool

A potential fix for floodfill in connectivity_sv erroring when running through an entity's _links table, due to said table being set to nil if the last link in that table happened to be removed

Also new tool (to be fleshed out later) to aid in seeing an entity's connections in various manners for CFW. Right now it requires 'developer 1' due to usage of debugoverlay, later an overlay can be made alongside networking for CFW info. Due to that requirement, the tool will not be listed in the menu and must be accessed alternatively, such as 'gmod_tool cfw_tool'

Author: LiddulBOFH

lua/cfw/classes/link_sv.lua

@@ -57,7 +57,6 @@ do -- Class def
             entA._links[indexB] = nil
 
             if not next(entA._links) then
-                entA._links = nil
                 entA:GetContraption():Sub(entA)
 
                 contraptionPopped = true
@@ -70,7 +69,6 @@ do -- Class def
             entB._links[indexA] = nil
 
             if not next(entB._links) then
-                entB._links = nil
                 entB:GetContraption():Sub(entB)
 
                 contraptionPopped = true

lua/weapons/gmod_tool/stools/cfw_tool.lua

@@ -0,0 +1,72 @@
+TOOL.Category	= "Contraption Framework"
+TOOL.Name		= "CFW Tool"
+TOOL.AddToMenu	= false
+
+
+--[[
+	To access this, use 'gmod_tool cfw_tool'
+	Hidden because this relies on developer 1, so not for use by normal means, for now
+	Eventually this will get fleshed out with multiple debug modes
+
+	For example:
+	Op 1 - Show entity's links via link table
+	Op 2 - Show contraption that this entity is a part of
+	Op 3 - ?
+
+	Tool screen should reflect mode of the tool as well
+	When this happens, maybe allow normal use of the tool as well?
+]]
+
+
+TOOL.Entity		= nil
+
+function TOOL:LeftClick(tr)
+	if not IsFirstTimePredicted() then return end
+	if CLIENT then return true end
+
+	if (not IsValid(tr.Entity)) or tr.Entity:IsWorld() then
+		self.Entity = nil
+	else
+		self.Entity	= tr.Entity
+	end
+
+	return true
+end
+
+function TOOL:Reload()
+	if not IsFirstTimePredicted() then return end
+	if CLIENT then return end
+
+	self.Entity = nil
+end
+
+function TOOL:Think()
+	local ent	= self.Entity
+	if not IsValid(ent) then return end
+	local selftbl	= ent:GetTable()
+
+	if not selftbl._links then return end
+
+	local tick = engine.TickInterval() + 0.05
+
+	local Rendered = {}
+	for _, link in pairs(selftbl._links) do
+		local entA, entB = link.entA, link.entB
+		debugoverlay.Line(entA:GetPos(),entB:GetPos(),tick,link.color,true)
+
+		if not Rendered[entA] then
+			debugoverlay.Text(entA:GetPos(),"A",tick,false)
+
+			Rendered[entA] = true
+		end
+
+		if not Rendered[entB] then
+			debugoverlay.Text(entB:GetPos(),"B",tick,false)
+			Rendered[entB] = true
+		end
+
+
+
+	end
+end
+