history: fix maxlen is defined as an optional argument even if it is not one

We now throw an assert is someone forgets to specify maxlen

1 files changed, 1 insertions, 0 deletions

diff --git a/ranger/container/history.py b/ranger/container/history.py
index 8300edae..c1d929ed 100644
--- a/ranger/container/history.py
+++ b/ranger/container/history.py
@@ -8,6 +8,7 @@ class HistoryEmptyException(Exception):
 
 class History(object):
     def __init__(self, maxlen=None, unique=True):
+        assert maxlen is not None, "maxlen cannot be None"
         if isinstance(maxlen, History):
             self._history = list(maxlen._history)
             self._index = maxlen._index