Fix in if reguarding pins.

lib/farmbot/celery_script/ast/node/_if.ex

@@ -11,10 +11,10 @@ defmodule Farmbot.CeleryScript.AST.Node.If do
 
     if is_number(left) or is_nil(left) do
       eval_if(left, op, rhs)
-      |> fn(result) ->
-        Logger.debug 2, "IF evaluated to #{result}."
-        result
-      end.() # for debug purposes.
+      # |> fn(result) ->
+      #   Logger.debug 2, "IF evaluated to #{inspect result}."
+      #   result
+      # end.() # for debug purposes.
       |> do_jump(else_, then_, env)
     else
       {:error, "Lefthand could not be evaluated to a number (#{inspect left})", env}
@@ -28,13 +28,14 @@ defmodule Farmbot.CeleryScript.AST.Node.If do
   defp eval_lhs({:pin, pin}) do
     case Farmbot.BotState.get_pin_value(pin) do
       {:ok, val} -> val
+      {:error, :unknown_pin} -> nil
       {:error, reason} -> {:error, reason}
     end
   end
 
   defp eval_if(nil, :is_undefined, _), do: true
   defp eval_if(_,   :is_undefined, _), do: false
-  defp eval_if(nil, _, _), do: {:error, "left hand side undefined."}
+  defp eval_if(nil, _, _), do: {:error, "Could not eval IF because left hand side of if statement is undefined."}
 
   defp eval_if(lhs, :>, rhs) when lhs > rhs, do: true
   defp eval_if(_lhs, :>, _rhs), do: false