Fix spurious '' token in suffix_list after capitalize() with no suffix

''.split(', ') returns [''] just like ''.split(' ') did for the other
attributes. Use a filtered list comprehension to preserve the comma
delimiter while dropping empty tokens, making suffix_list consistent
with the [] invariant the rest of the codebase relies on.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: derek73

nameparser/parser.py

@@ -989,7 +989,7 @@ def capitalize(self, force: bool | None = None) -> None:
         self.middle_list = self.cap_piece(self.middle, 'middle').split()
         self.last_list = self.cap_piece(self.last, 'last').split()
         # suffix is stored comma-separated ("Ph.D., J.D."), not space-separated
-        self.suffix_list = self.cap_piece(self.suffix, 'suffix').split(', ')
+        self.suffix_list = [s for s in self.cap_piece(self.suffix, 'suffix').split(', ') if s]
 
     def handle_capitalization(self) -> None:
         """

tests/test_capitalization.py

@@ -76,6 +76,23 @@ def test_capitalize_title_and_last_only_no_spurious_tokens(self) -> None:
         self.assertEqual(hn.middle_list, [])
         self.m(str(hn), 'Dr Doe', hn)
 
+    def test_capitalize_empty_suffix_produces_no_spurious_tokens(self) -> None:
+        # ''.split(', ') returns [''] just like ''.split(' ') did for the other
+        # attributes — an absent suffix should produce suffix_list == [], not [''].
+        hn = HumanName('JOHN DOE')
+        hn.capitalize()
+        self.assertEqual(hn.suffix_list, [])
+
+    def test_capitalize_single_suffix_still_works(self) -> None:
+        hn = HumanName('JOHN DOE PHD')
+        hn.capitalize()
+        self.assertEqual(hn.suffix_list, ['Ph.D.'])
+
+    def test_capitalize_multiple_suffixes_still_split_correctly(self) -> None:
+        hn = HumanName('JOHN DOE PHD MD')
+        hn.capitalize()
+        self.assertEqual(hn.suffix_list, ['Ph.D.', 'M.D.'])
+
     # Leaving already-capitalized names alone
     def test_no_change_to_mixed_chase(self) -> None:
         hn = HumanName('Shirley Maclaine')