Resolve "Score of order depends on remaining time"

Closes #128 (closed)

cooperative_cuisine/scores.py

@@ -120,10 +120,10 @@ def stepped_score(
         raise ValueError("steps and vals must have the same length")
 
     for threshold, ratio in zip(reversed(steps), reversed(score_ratios)):
-        if time_percentage >= threshold:
+        if max(time_percentage, 0) >= threshold:
             return float(np.round(max_score * ratio, decimals=round_decimals))
 
-    assert False, "Should not reach here."
+    assert False, "This should not happen."
 
 
 class ScoreViaHooks(HookCallbackClass):