Fix perfect match missed for headers with empty values: add test and changelog

Author: Kriechi

CHANGELOG.rst

@@ -17,6 +17,7 @@ dev
 **Bugfixes**
 
 - Headers marked as `sensitive` will no longer log their value at DEBUG level. Instead a placeholder value of `SENSITIVE_REDACTED` is logged.
+- Fixed perfect match missed for headers with empty values.
 
 4.1.0 (2025-01-22)
 ------------------

tests/test_hpack.py

@@ -126,6 +126,18 @@ def test_indexed_header_field(self):
         assert e.encode(header_set, huffman=False) == result
         assert list(e.header_table.dynamic_entries) == []
 
+    def test_indexed_header_field_empty_value_string(self):
+        """
+        The header field representation uses an indexed header field, from
+        the static table.
+        """
+        e = Encoder()
+        header_set = {':authority': ''}
+        result = b'\x81'
+
+        assert e.encode(header_set, huffman=False) == result
+        assert list(e.header_table.dynamic_entries) == []
+
     def test_indexed_header_field_from_static_table(self):
         e = Encoder()
         e.header_table_size = 0