fix for GRAILS-10820 "Group UrlMappings Producing null Params"
Revert "Fix GRAILS-10763 problem with comments inside UrlMappings configuration"

This reverts commit c9611154af1c5dd7d5141a9e582200c1cd0a122a.

Conflicts:
	grails-plugin-url-mappings/src/main/groovy/org/codehaus/groovy/grails/plugins/web/mapping/UrlMappingsGrailsPlugin.groovy
	grails-test-suite-uber/src/test/groovy/org/codehaus/groovy/grails/plugins/web/mapping/UrlMappingsGrailsPluginTests.groovy
Fix NPE in DomainClassMarshaller

I found an NPE in DomainClassMarshaller which is caused by changes in JSONWriter in commit 0aa1ec82ba236cac3f8cf6d4c139b67a26a19b3c.  A call to writer.value(null) causes JSONWriter.value(Number) to be called, which in turn throws the NPE. In that commit method valueNull() was introduced, so I use it instead.

I'm not sure if line 160 (json.value(null)) must be changed, too.
Merge pull request #429 from dellermann/patch-1

Fix NPE in DomainClassMarshaller
GRAILS-10799 related: Fix NPEs in JSONWriter
GRAILS-10799 related: Test null handling in JSONWriter
Fixed for GRAILS-9778 - Cygwin shows empty path
Merge branch '2.3.x'