reproduce fuzzing error

see https://github.com/collective/icalendar/pull/577#discussion_r1382441779

src/icalendar/tests/test_oss_fuzz_errors.py

@@ -0,0 +1,9 @@
+"""This file collects errors that the OSS FUZZ build has found."""
+from icalendar import Calendar
+import pytest
+
+
+def test_stack_is_empty():
+    """If we get passed an invalid string, we expect to get a ValueError."""
+    with pytest.raises(ValueError):
+        Calendar.from_ical("END:CALENDAR")