don't hide errors when driver.love connects

The intent of hiding errors is to see if a code change I made improved
things. But many commands from the driver don't involve a code change.
It seems more useful to leave the error up in those situations.

live.lua

@@ -77,8 +77,10 @@ function live.update(dt)
   if Current_time - Live.previous_read > 0.1 then
     local buf = live.receive_from_driver()
     if buf then
-      live.run(buf)
-      Mode = 'run'
+      local possibly_mutated = live.run(buf)
+      if possibly_mutated then
+        Mode = 'run'
+      end
       if on.code_change then on.code_change() end
     end
     Live.previous_read = Current_time
@@ -130,7 +132,7 @@ function reset_terminal()
   return '\027[m'
 end
 
--- define or undefine top-level bindings
+-- returns true if we might have mutated the app, by either creating or deleting a definition
 function live.run(buf)
   local cmd = live.get_cmd_from_buffer(buf)
   assert(cmd)
@@ -159,6 +161,7 @@ function live.run(buf)
       Live.filename[definition_name] = nil
     end
     live.send_to_driver('{}')
+    return true
   elseif cmd == 'GET' then
     local definition_name = buf:match('^%s*%S+%s+(%S+)')
     local val, _ = live.get_binding(definition_name)
@@ -219,13 +222,14 @@ function live.run(buf)
       if err2 then
         -- throw an error
         live.send_to_driver('ERROR '..tostring(err..'\n\n'..err2))
-        return
+        return true
       end
     end
     -- run all tests
     Test_errors = {}
     App.run_tests(record_error_by_test)
     live.send_to_driver(json.encode(Test_errors))
+    return true
   end
 end