Validator doesn't show errors when panel is not open

[GerdP]

What steps will reproduce the problem?

1. Start JOSM
2. Crtl+N for new Edit Layer
3. If Validator Panel is opened, close it and the data layer and open a new data layer
4. Draw a way without adding any tags and run Validator

What is the expected result?

Validator panel should open and show a warning for an untagged way

What happens instead?

Validator panel opens but shows no erros.

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

Executing the validator again shows the expected result. Same problem happens when data is downloaded.
The problem is that ValidatorTreePanel.buildTree() is called twice, once with the error list and again with an still empty error list retrieved from MainApplication.getLayerManager().getEditLayer().validationErrors
I did not find the best place to fix that.

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2018-12-31 15:09:58 +0100 (Mon, 31 Dec 2018)
Build-Date:2018-12-31 14:24:10
Revision:14620
Relative:URL: ^/trunk

Identification: JOSM/1.5 (14620 de) Windows 10 64-Bit
OS Build number: Windows 10 Home 1803 (17134)
Memory Usage: 553 MB / 1820 MB (364 MB allocated, but free)
Java version: 1.8.0_191-b12, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: \Display0 1920x1080
Maximum Screen Size: 1920x1080

Plugins:
+ OpeningHoursEditor (34535)
+ apache-commons (34506)
+ buildings_tools (34807)
+ download_along (34503)
+ ejml (34389)
+ geotools (34513)
+ jaxb (34506)
+ jts (34524)
+ o5m (34405)
+ opendata (34805)
+ pbf (34576)
+ poly (34546)
+ reltoolbox (34788)
+ reverter (34552)
+ utilsplugin2 (34793)

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.
- W: Region [TMS_BLOCK_v2] Resetting cache
- W: Cannot start IPv4 remotecontrol https server on port 8112: Keystore was tampered with, or password was incorrect
- W: Cannot start IPv6 remotecontrol https server on port 8112: Keystore was tampered with, or password was incorrect

[GerdP]

In 14666/josm:

fix #17183: unfurl Validator Panel first and set error list later so that unfurl doesn't empty the error list