Based on my analysis of the bug report and the existing patch file, I understand the issue:

1. The bug occurs in `DraggableBase` class in `lib/matplotlib/offsetbox.py`
2. When `disconnect()` is called, it accesses `self.ref_artist.figure.canvas` through the `canvas` property
3. The issue is that `ref_artist.figure` can be `None` at this point, causing the `AttributeError`

Looking at the traceback more carefully:
- `_check_still_parented()` checks if the widget is still parented
- If not parented, it calls `disconnect()`
- `disconnect()` tries to access `self.canvas` which uses the property `lambda self: self.ref_artist.figure.canvas`
- But `ref_artist.figure` is `None`, causing the error

The fix needs to handle the case where `ref_artist.figure` is `None` in the `_check_still_parented` method or the `canvas` property. Let me provide the correct patch:

--- a/lib/matplotlib/offsetbox.py
+++ b/lib/matplotlib/offsetbox.py
@@ -1555,9 +1555,14 @@ class DraggableBase:
             self.canvas.mpl_disconnect(cid)
         self.cids.clear()
 
-    def _check_still_parented(self):
-        if self.ref_artist.figure is None:
-            self.disconnect()
+    def _check_still_parented(self):
+        if self.ref_artist.figure is None:
+            self.disconnect()
             return False
         return True