BUG: Guard empty input to prevent IndexError (#3448)

Closes #3446.

Author: KyleJung0828

pypdf/_utils.py

@@ -77,7 +77,7 @@
 
 def parse_iso8824_date(text: Optional[str]) -> Optional[datetime]:
     orgtext = text
-    if text is None:
+    if not text:
         return None
     if text[0].isdigit():
         text = "D:" + text

tests/test_utils.py

@@ -360,6 +360,18 @@ def test_parse_datetime(text, expected):
     assert date_str == expected
 
 
+@pytest.mark.parametrize(
+    ("text", "expected"),
+    [
+        ("", None),
+        (None, None),
+    ],
+)
+def test_parse_datetime_edge_cases(text, expected):
+    date = parse_iso8824_date(text)
+    assert date == expected
+
+
 def test_parse_datetime_err():
     with pytest.raises(ValueError) as ex:
         parse_iso8824_date("D:20210408T054711Z")