Fix NULL error in wire_adv tool (#3075)

* Fix NULL error

* Use tab indentation

* Fix linter warning

lua/weapons/gmod_tool/stools/wire_adv.lua

@@ -620,6 +620,11 @@ elseif CLIENT then
 		end
 
 		if self:GetStage() == 2 then
+			if not IsValid( self.CurrentEntity ) then
+				self:SetStage(0)
+				return
+			end
+
 			local _, outputs = self:GetPorts( self.CurrentEntity )
 
 			if alt then -- Auto wiring
@@ -966,7 +971,7 @@ elseif CLIENT then
 			end
 			return true
 		elseif name == "Selected" and self:GetStage() == 2 then
-			local inputs, outputs = self:GetPorts( ent )
+			local _, outputs = self:GetPorts( ent )
 			if not isTableEmpty(outputs) then return false end
 			if self:GetOwner():KeyDown( IN_WALK ) then -- Gray out the ones that won't be able to be wired to any input
 				for i=1,#outputs do