Rules validation throws exception instead or warning

[skyper]

What steps will reproduce the problem?

1. (Re-)Load a broken rule file containing backslashes '\' in the assertMatch values can cause this exception.

What is the expected result?

Message including the line and the position of the problem but no BugReportHandler

What happens instead?

BugReportHandler

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

After that, JOSM stops to automatically reload the rule file.
Do not get the BugReportHandler all the time but the exception on the console.

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-07-06 23:02:10 +0200 (Mon, 06 Jul 2020)
Revision:16738
Build-Date:2020-07-07 01:30:48
URL:https://josm.openstreetmap.de/svn/trunk

Plugins:
+ tagging-preset-tester (35267)

Validator rules:
+ ${HOME}/JOSM/validator/GTFS_rules.mapcss

Last errors/warnings:
- E: Handled by bug report queue: java.lang.IllegalArgumentException: Expecting n/node/w/way/r/relation/area, but got '"node'


=== REPORTED CRASH DATA ===
BugReportExceptionHandler#handleException:
No data collected.

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: File Watcher (23)
java.lang.IllegalArgumentException: Expecting n/node/w/way/r/relation/area, but got '"node'
	at org.openstreetmap.josm.data.osm.OsmUtils.createPrimitive(OsmUtils.java:171)
	at org.openstreetmap.josm.data.validation.tests.MapCSSTagCheckerAsserts.checkAsserts(MapCSSTagCheckerAsserts.java:60)
	at org.openstreetmap.josm.data.validation.tests.MapCSSTagChecker$TagCheck.ofMapCSSRule(MapCSSTagChecker.java:344)
	at org.openstreetmap.josm.data.validation.tests.MapCSSTagChecker$TagCheck.readMapCSS(MapCSSTagChecker.java:366)
	at org.openstreetmap.josm.data.validation.tests.MapCSSTagChecker.addMapCSS(MapCSSTagChecker.java:790)
	at org.openstreetmap.josm.data.validation.tests.MapCSSTagChecker.addMapCSS(MapCSSTagChecker.java:778)
	at org.openstreetmap.josm.data.validation.tests.MapCSSTagChecker.reloadRule(MapCSSTagChecker.java:858)
	at org.openstreetmap.josm.io.FileWatcher.processEvents(FileWatcher.java:160)
	at java.base/java.lang.Thread.run(Thread.java:834)

[skyper]

Oh. an odd number of " in the assertMatch triggers this, too.

[skyper]

See #19685 for another exception raised by validation an incorrect rule.