fix `repr()` & `format_dict` when disabled

- fixes #624

tqdm/std.py

@@ -10,7 +10,7 @@ Usage:
 from __future__ import absolute_import, division
 
 import sys
-from collections import OrderedDict
+from collections import OrderedDict, defaultdict
 from contextlib import contextmanager
 from datetime import datetime, timedelta
 from numbers import Number
@@ -1420,14 +1420,16 @@ class tqdm(Comparable):
     @property
     def format_dict(self):
         """Public API for read-only member access."""
+        if self.disable and not hasattr(self, 'unit'):
+            return defaultdict(lambda: None, {
+                'n': self.n, 'total': self.total, 'elapsed': 0, 'unit': 'it'})
         if self.dynamic_ncols:
             self.ncols, self.nrows = self.dynamic_ncols(self.fp)
-        ncols, nrows = self.ncols, self.nrows
         return {
             'n': self.n, 'total': self.total,
             'elapsed': self._time() - self.start_t if hasattr(self, 'start_t') else 0,
-            'ncols': ncols, 'nrows': nrows, 'prefix': self.desc, 'ascii': self.ascii,
-            'unit': self.unit, 'unit_scale': self.unit_scale,
+            'ncols': self.ncols, 'nrows': self.nrows, 'prefix': self.desc,
+            'ascii': self.ascii, 'unit': self.unit, 'unit_scale': self.unit_scale,
             'rate': self._ema_dn() / self._ema_dt() if self._ema_dt() else None,
             'bar_format': self.bar_format, 'postfix': self.postfix,
             'unit_divisor': self.unit_divisor, 'initial': self.initial,