Address liteary form control field bug

Why these changes are being introduced:

There is at least one MARC record that comes through
where control field 008 is not 34 characters, and therefore
was throwing an error when we attempt to grab the 33rd character.

How this addresses that need:
* If control field 008 is < 34 chars, return None for literary form

Side effects of this change:
* Transmogrifier runs for large swaths of files, e.g. full runs, will
not catastrophically fail for this single bug.
* This might suggest another layer of error handling to avoid full
run failure for a single record, will create at ticket for this.

Relevant ticket(s):
* https://mitlibraries.atlassian.net/browse/TIMX-355

pyproject.toml

@@ -4,7 +4,7 @@ line-length = 90
 [tool.mypy]
 disallow_untyped_calls = true
 disallow_untyped_defs = true
-exclude = ["tests/"]
+exclude = ["tests/", "output/"]
 
 [tool.pytest.ini_options]
 log_level = "INFO"

tests/sources/xml/test_marc.py

@@ -1349,6 +1349,13 @@ def test_get_literary_form_transforms_correctly_if_char_positions_blank():
     assert Marc.get_literary_form(source_record) is None
 
 
+def test_get_literary_form_returns_none_if_control_field_too_short():
+    source_record = create_marc_source_record_stub(
+        control_field_insert='<controlfield tag="008">i_am_very_short</controlfield>',
+    )
+    assert Marc.get_literary_form(source_record) is None
+
+
 def test_get_links_success():
     source_record = create_marc_source_record_stub(
         datafield_insert=(

transmogrifier/sources/xml/marc.py

@@ -586,10 +586,15 @@ def get_literary_form(cls, source_record: Tag) -> str | None:
         and Leader/07 (Bibliographic level) contains code
         a (Monographic component part), c (Collection), d (Subunit),
         or m (Monograph).
+
+        If control field 008 is shorter than 34 characters, return None as we cannot
+        accurately determine.
         """
         leader_field = cls._get_leader_field(source_record)
         control_field = cls._get_control_field(source_record)
         if leader_field[6] in "at" and leader_field[7] in "acdm":
+            if len(control_field) <= 33:  # noqa: PLR2004
+                return None
             if control_field[33] in "0se":
                 return "Nonfiction"
             return "Fiction"