fix empty list omitted bug

Author: sn6uv

mathics/builtin/evaluation.py

@@ -413,6 +413,8 @@ class OutputSizeLimit(Predefined):
     >> Table[i, {i, 1, 100}]
      = {1, <<98>>, 100}
     >> $OutputSizeLimit = 1000;
+    #> {}
+     = {}
     """
 
     name = '$OutputSizeLimit'

mathics/core/expression.py

@@ -2380,7 +2380,7 @@ def make(self, items, form, segment=None):
         capacity = state.capacity
 
         if capacity is None or len(items) < 1:
-            return self._unlimited(items, form, segment)
+            return self._unlimited.make(items, form, segment)
 
         left_leaves = []
         right_leaves = []