fix training without an unperturbed trial

main.lua

@@ -226,6 +226,7 @@ local function load_next_trial()
     end
     trial_i = trial_i + 1
     if trial_i == 0 and not cfg.unperturbed_trial then
+        trial_neg = false
         trial_i = 1
     end
     if trial_i > 0 then