fix #2800

mitmproxy/contentviews/base.py

@@ -49,8 +49,9 @@ def format_dict(
     ]
     entries, where key is padded to a uniform width.
     """
-    max_key_len = max(len(k) for k in d.keys())
-    max_key_len = min(max_key_len, KEY_MAX)
+
+    max_key_len = max((len(k) for k in d.keys()), default=0)
+    max_key_len = min((max_key_len, KEY_MAX), default=0)
     for key, value in d.items():
         if isinstance(key, bytes):
             key += b":"

test/mitmproxy/contentviews/test_base.py

@@ -1 +1,17 @@
-# TODO: write tests
+import pytest
+from mitmproxy.contentviews import base
+
+
+def test_format_dict():
+    d = {"one": "two", "three": "four"}
+    f_d = base.format_dict(d)
+    assert next(f_d)
+
+    d = {"adsfa": ""}
+    f_d = base.format_dict(d)
+    assert next(f_d)
+
+    d = {}
+    f_d = base.format_dict(d)
+    with pytest.raises(StopIteration):
+        next(f_d)