Fix possible use-after-free in VerticalLayout.

If some row widgets of VerticalLayout are living
in its own lifetime() we have a use-after-free.

Because this lifetime() destroys this child row
already after ~VerticalLayout which can call back
into VerticalLayout::childHeightUpdated (the subscription
lives inside the same lifetime() as well) which
will access _rows member that was already destroyed.

Now all subscriptions die before _rows are destroyed.

ui/wrap/vertical_layout.cpp

@@ -133,7 +133,7 @@ RpWidget *VerticalLayout::insertChild(
 			}
 		}, [=] {
 			removeChild(weak);
-		}, lifetime());
+		}, _rowsLifetime);
 		return weak;
 	}
 	return nullptr;

ui/wrap/vertical_layout.h

@@ -82,6 +82,8 @@ private:
 	std::vector<Row> _rows;
 	bool _inResize = false;
 
+	rpl::lifetime _rowsLifetime;
+
 };
 
 } // namespace Ui