Fixed #30274 -- Prevented segmentation fault on LineString iteration.

This reverts commit 138a78ec8c and adds
a test for the regression.

django/contrib/gis/geos/linestring.py

@@ -91,7 +91,8 @@ class LineString(LinearGeometryMixin, GEOSGeometry):
 
     def __iter__(self):
         "Allow iteration over this LineString."
-        return iter(self._cs)
+        for i in range(len(self)):
+            yield self[i]
 
     def __len__(self):
         "Return the number of points in this LineString."

tests/gis_tests/geos_tests/test_geos.py

@@ -1434,3 +1434,12 @@ class GEOSTest(SimpleTestCase, TestDataMixin):
         self.assertEqual(p.transform(2774, clone=True), Point(srid=2774))
         p.transform(2774)
         self.assertEqual(p, Point(srid=2774))
+
+    def test_linestring_iter(self):
+        ls = LineString((0, 0), (1, 1))
+        it = iter(ls)
+        # Step into CoordSeq iterator.
+        next(it)
+        ls[:] = []
+        with self.assertRaises(IndexError):
+            next(it)