fix for GRAILS-8572 "Rendering a Command Object as JSON causes ArrayIndexOutOfBoundException"
Merge branch '2.1.x' into 2.2.x

Conflicts:
	grails-web/src/main/groovy/org/codehaus/groovy/grails/web/binding/DefaultASTDatabindingHelper.java
Merge branch '2.2.x'