ROB: Fix compression issues for removed images which might be None (#3246)

Closes #3237.

Author: stefan6419846

pypdf/_writer.py

@@ -1650,8 +1650,9 @@ def replace_in_obj(
         orphans = [True] * len(self._objects)
         # look for similar objects
         for idx, obj in enumerate(self._objects):
-            if obj is None:
+            if is_null_or_none(obj):
                 continue
+            assert obj is not None  # mypy: TypeGuard of `is_null_or_none` does not help here.
             assert isinstance(obj.indirect_reference, IndirectObject)
             h = obj.hash_value()
             if remove_identicals and h in self._idnum_hash:

tests/test_writer.py

@@ -2668,3 +2668,10 @@ def test_incremental_read():
     # 2 = Pages, 5 = New Page, 6 = XRef, Size == 7
     # XRef is created on write and not counted
     assert len(writer._objects) == 5
+
+
+def test_compress_identical_objects__after_remove_images():
+    """Test for #3237"""
+    writer = PdfWriter(clone_from=RESOURCE_ROOT / "AutoCad_Diagram.pdf")
+    writer.remove_images()
+    writer.compress_identical_objects(remove_identicals=True, remove_orphans=True)