BUG: Remove erroneous assertion check (#1564)

Closes #1559

This is due to a bad interpretation of text at bottom of page 108 of PDF 1.7 reference

pypdf/_reader.py

@@ -1901,11 +1901,11 @@ def _read_xref_subsections(
         get_entry: Callable[[int], Union[int, Tuple[int, ...]]],
         used_before: Callable[[int, Union[int, Tuple[int, ...]]], bool],
     ) -> None:
-        last_end = 0
+        # last_end = 0
         for start, size in self._pairs(idx_pairs):
             # The subsections must increase
-            assert start >= last_end
-            last_end = start + size
+            # assert start >= last_end
+            # last_end = start + size
             for num in range(start, start + size):
                 # The first entry is the type
                 xref_type = get_entry(0)

tests/test_reader.py

@@ -1279,3 +1279,11 @@ def test_build_outline_item(caplog):
 def test_page_labels(src, page_labels):
     max_indices = 6
     assert PdfReader(src).page_labels[:max_indices] == page_labels[:max_indices]
+
+
+def test_iss1559():
+    url = "https://github.com/py-pdf/pypdf/files/10441992/default.pdf"
+    name = "iss1559.pdf"
+    reader = PdfReader(BytesIO(get_pdf_from_url(url, name=name)))
+    for p in reader.pages:
+        p.extract_text()