Try to fix yield from GC issues

Make sure we always update root and parent references before
releasing the old root object.

This fixes some crashes under aggressive cycle collection, so
hopefully this will also fix bug #75351.

Author: nikic

Zend/zend_generators.c

@@ -179,10 +179,11 @@ static void zend_generator_dtor_storage(zend_object *object) /* {{{ */
 		zend_generator *root = generator->node.ptr.root, *next;
 		while (UNEXPECTED(root != generator)) {
 			next = zend_generator_get_child(&root->node, generator);
+			generator->node.ptr.root = next;
+			next->node.parent = NULL;
 			OBJ_RELEASE(&root->std);
 			root = next;
 		}
-		generator->node.parent = NULL;
 	}
 
 	if (EXPECTED(!ex) || EXPECTED(!(ex->func->op_array.fn_flags & ZEND_ACC_HAS_FINALLY_BLOCK))
@@ -664,11 +665,12 @@ ZEND_API zend_generator *zend_generator_update_current(zend_generator *generator
 		}
 	}
 
+	leaf->node.ptr.root = root;
 	if (old_root) {
 		OBJ_RELEASE(&old_root->std);
 	}
 
-	return leaf->node.ptr.root = root;
+	return root;
 }
 
 static int zend_generator_get_next_delegated_value(zend_generator *generator) /* {{{ */