Improve handling of missing images when loading a session with image layers

[GerdP]

What steps will reproduce the problem?

1. start JOSM
2. drag&drop some *.jpg files, in my case 218
3. save session as test.jos
4. close layer
5. rename or remove some of the images that were dropped
6. load session test.jos which now refers to unavailable images

What is the expected result?

The session is loaded and maybe a popup dialog asks if I want to remove or skip invalid references.
Something similar happens when my session contains a gpx layer and the corresponding gpx file was removed.

What happens instead?

JOSM silently loads the session and tries to load non-existing images. I have to click the trashcan icon for each non-existing image and I have to remember to save the session afterwards.

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

I assume it would slow down the load if JOSM would check each image for existence, esp. when the layer contains references to network files. So maybe just implement a new action "Cleanup session"?

Build-Date:2024-01-19 17:43:59
Revision:18947
Is-Local-Build:true

Identification: JOSM/1.5 (18947 SVN en) Windows 10 64-Bit
OS Build number: Windows 10 Home 2009 (19045)
Memory Usage: 484 MB / 1678 MB (139 MB allocated, but free)
Java version: 1.8.0_272-b10, AdoptOpenJDK, OpenJDK 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920×1080 (scaling 1.00×1.00)
Maximum Screen Size: 1920×1080
Best cursor sizes: 16×16→32×32, 32×32→32×32
System property file.encoding: UTF-8
System property sun.jnu.encoding: Cp1252
Locale info: en_DE
Numbers with default locale: 1234567890 -> 1234567890
VM arguments: [-agentlib:jdwp=transport=dt_socket,suspend=y,address=localhost:51233, -ea, -javaagent:D:\eclipse-java-2020-09\eclipse\configuration\org.eclipse.osgi\3245\0\.cp\lib\javaagent-shaded.jar, -Dfile.encoding=UTF-8, -Dstdout.encoding=UTF-8, -Dstderr.encoding=UTF-8]
Program arguments: [--language=en, --debug]

Plugins:
+ OpeningHoursEditor (36196)
+ RoadSigns (36196)
+ apache-commons (36176)
+ buildings_tools (36200)
+ comfort0 (36200)
+ o5m (36126)
+ pbf (36176)
+ poly (36126)
+ reltoolbox (36200)
+ reverter (36196)
+ undelete (36126)
+ utilsplugin2 (36200)

Validator rules:
+ c:\josm\core\resources\data\validator\combinations.mapcss
+ c:\josm\core\resources\data\validator\geometry.mapcss
+ c:\josm\core\resources\data\validator\relation.mapcss
+ c:\josm\core\resources\data\validator\unnecessary.mapcss
+ d:\java_tools\JOSM\mygeometry.mapcss
+ https://josm.openstreetmap.de/josmfile?page=Rules/GermanySpecific&zip=1

Last errors/warnings:
- 00444.705 E: Failed to locate image 'Flag, Blue'
- 00491.583 E: Failed to locate image 'Flag, Blue'
- 00552.779 E: Failed to locate image 'Flag, Blue'
- 00552.780 E: Failed to locate image 'Flag, Blue'
- 00552.782 E: Failed to locate image 'Flag, Blue'
- 00574.089 E: java.io.FileNotFoundException: F:\osm\bilder\2024-01-16\DSC_4803.JPG (Das System kann die angegebene Datei nicht finden)
- 00577.934 E: java.io.FileNotFoundException: F:\osm\bilder\2024-01-16\DSC_4803.JPG (Das System kann die angegebene Datei nicht finden)
- 00694.395 E: Failed to locate image 'Flag, Blue'
- 00694.397 E: Failed to locate image 'Flag, Blue'
- 00694.399 E: Failed to locate image 'Flag, Blue'