NullPointerExpection when trying to write an constrained condition-group

[NLueg]

Expected Behavior

In case of a falsy rule, I would expect to get a informative message.

Current Behavior

For following rule, I get a NullPointerExpection in the parsing-process

name must equals place or 

Here the stacktrace that I got:

io.openvalidation.common.utils.ThrowingConsumer.accept(ThrowingConsumer.java:29)
java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
io.openvalidation.antlr.transformation.TransformerBase.eachTreeChild(TransformerBase.java:50)
io.openvalidation.antlr.transformation.TransformerBase.eachTreeChild(TransformerBase.java:44)
io.openvalidation.antlr.transformation.parsetree.PTRuleConstrainedTransformer.transform(PTRuleConstrainedTransformer.java:62)
io.openvalidation.antlr.transformation.parsetree.PTRuleConstrainedTransformer.transform(PTRuleConstrainedTransformer.java:33)
io.openvalidation.antlr.transformation.TransformerBase.createASTItem(TransformerBase.java:64)
io.openvalidation.antlr.transformation.parsetree.PTModelTransformer.lambda$transform$1(PTModelTransformer.java:52)
io.openvalidation.common.utils.ThrowingConsumer.accept(ThrowingConsumer.java:27)
java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
io.openvalidation.antlr.transformation.TransformerBase.eachTreeChild(TransformerBase.java:50)
io.openvalidation.antlr.transformation.TransformerBase.eachTreeChild(TransformerBase.java:44)
io.openvalidation.antlr.transformation.parsetree.PTModelTransformer.transform(PTModelTransformer.java:45)
io.openvalidation.antlr.MainASTBuildListener.exitMain(MainASTBuildListener.java:45)
io.openvalidation.antlr.generated.mainParser$MainContext.exitRule(mainParser.java:143)
org.antlr.v4.runtime.Parser.triggerExitRuleEvent(Parser.java:408)
org.antlr.v4.runtime.Parser.exitRule(Parser.java:642)
io.openvalidation.antlr.generated.mainParser.main(mainParser.java:279)
io.openvalidation.antlr.ANTLRExecutor.run(ANTLRExecutor.java:52)
io.openvalidation.antlr.ANTLRExecutor.run(ANTLRExecutor.java:34)
io.openvalidation.antlr.OpenValidationANTLRParser.parse(OpenValidationANTLRParser.java:29)
io.openvalidation.core.Engine.parse(Engine.java:101)
io.openvalidation.core.Engine.generateCode(Engine.java:75)
io.openvalidation.core.OpenValidation.generateCode(OpenValidation.java:144)
io.openvalidation.core.OpenValidation.generateCode(OpenValidation.java:85)
io.openvalidation.core.OpenValidation.generate(OpenValidation.java:67)
io.openvalidation.rest.service.OpenValidationServiceImpl.generate(OpenValidationServiceImpl.java:46)
io.openvalidation.rest.controller.LintingController.generate(LintingController.java:50)
jdk.internal.reflect.GeneratedMethodAccessor99.invoke(Unknown Source)
java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.base/java.lang.reflect.Method.invoke(Method.java:566)
org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:189)
org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797)
org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:908)
javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200)
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.base/java.lang.Thread.run(Thread.java:834)

Possible Solution

Complete the rule manually

Steps to Reproduce (for bugs)

1. Parse the given rule with the culture en and the language Java

Context

I wanted to implement code-completion for constrained rules.
This is not possible with this error.

[jages]

Another case for the need to improve error reporting on incomplete rules.