bugfix: wasn't recovering from errors

Bug was introduced in commit a2451aa26 32 hours ago, because I didn't go
over the manual tests for the error-handling protocol after modifying
the error-handling protocol. (I only tested them in template-live.)

Manual_tests.md

@@ -63,9 +63,7 @@ record those here.
     on.draw = function(
     ```
   Hit F4. Driver shows an error under the definition as before.
-  Quit the client app. The invalid code is saved in file 0002-on.draw in the
-  save dir. However, the file 'head' in the save dir contains '1'.
-  [Don't restart the client app.]
+  Quit the client app.
   Switch back to the driver. Hit F4. The driver hangs and needs to be
   force-quit. [This is not ideal, but how things are today.]
 

main.lua

@@ -153,7 +153,6 @@ function App.draw()
 end
 
 function App.update(dt)
-  if Mode == 'error' then return end
   Current_time = Current_time + dt
   -- some hysteresis while resizing
   if Current_time < Last_resize_time + 0.1 then