Don't call show_feature if context key is invalid

Author: Tom

feature_flipper/templatetags/feature_flipper.py

@@ -43,8 +43,11 @@ def render(self, context):
         """
         user = self._get_value(self.user_key, context)
         feature = self._get_value(self.feature, context)
-        allowed = show_feature(user, feature)
 
+        if feature is None:
+            return ''
+
+        allowed = show_feature(user, feature)
         return self.nodelist.render(context) if allowed else ''
 
     def _get_value(self, key, context):
@@ -57,4 +60,4 @@ def _get_value(self, key, context):
             return key[1:-1]
         if key in string.digits:
             return int(key)
-        return context.get(key, False)
+        return context.get(key, None)