Close button doesn't cancel edits & doesn't add to undo list

[Famlam]

What steps will reproduce the problem?

1. Have turnlanes-tagging installed
2. Select any road without turn:lanes or lanes
3. Open turn lanes editor, click random at some turn lane icons
4. press the close button

What is the expected result?

Edits are reverted when pressing the close [X] button (top right in Windows)

What happens instead?

• Edits remain
• (Undo doesn't revert these edits either: the icon stays grayed out)

Please provide any additional information below. Attach a screenshot if possible.

Note that the Cancel button and/or Esc does work as expected

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-10-03 13:42:38 +0200 (Sat, 03 Oct 2020)
Build-Date:2020-10-04 01:30:47
Revision:17084
Relative:URL: ^/trunk

Identification: JOSM/1.5 (17084 nl) Windows 10 64-Bit
OS Build number: Windows 10 Home 2004 (19041)
Memory Usage: 827 MB / 1820 MB (435 MB allocated, but free)
Java version: 1.8.0_271-b09, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920x1080 (scaling 1.0x1.0)
Maximum Screen Size: 1920x1080
Best cursor sizes: 16x16 -> 32x32, 32x32 -> 32x32
Dataset consistency test: No problems found

Plugins:
+ OpeningHoursEditor (35414)
+ imagery_offset_db (35405)
+ pt_assistant (2.1.10-80-g7d9bba3)
+ reverter (35556)
+ tageditor (35258)
+ turnlanes-tagging (283)
+ undelete (35521)
+ utilsplugin2 (35487)

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/PublicTransport&zip=1
+ %UserProfile%\Documents\tijdelijke bestanden\josm-eigen.mappaint.mapcss

Validator rules:
+ %UserProfile%\Documents\tijdelijke bestanden\josm-eigen.validator.mapcss