False positive warning on source:*:conditional

[gaben]

What steps will reproduce the problem?

1. Tag a way with source:maxspeed:conditional=sign
2. Run the validator

What is the expected result?

No warning. The key describes the source of the conditional maxspeed limit, similar to source:maxspeed.

What happens instead?

The validator complaining, saying the key is invalid.

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

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2023-09-21 20:54:28 +0200 (Thu, 21 Sep 2023)
Build-Date:2023-09-22 01:30:58
Revision:18841
Relative:URL: ^/trunk

Identification: JOSM/1.5 (18841 hu) Windows 10 64-Bit
OS Build number: Windows 10 Pro for Workstations 2009 (19045)
Memory Usage: 867 MB / 7266 MB (285 MB allocated, but free)
Java version: 1.8.0_382-b05, Azul Systems, Inc., OpenJDK 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920×1200 (scaling 1.00×1.00) \Display1 1200×1920 (scaling 1.00×1.00)
Maximum Screen Size: 1920×1920
Best cursor sizes: 16×16→32×32, 32×32→32×32
System property file.encoding: Cp1250
System property sun.jnu.encoding: Cp1250
Locale info: hu_HU
Numbers with default locale: 1234567890 -> 1234567890
VM arguments: [-Dicedtea-web.bin.name=javaws.exe, -Dicedtea-web.bin.location=C:\Program Files\IcedTeaWeb\WebStart\bin\javaws.exe]
Dataset consistency test: No problems found