Description of problem:
When a user creates a new task directly through the Tasks List page in the Business Central it is not possible to manipulate this task through the REST API.

Version-Release number of selected component (if applicable):
6.0.1 ER1

Steps to Reproduce:
1. Create a new task on the Tasks List page.
2. Try to get task details using REST: http://localhost:8080/business-central/rest/task/

Actual results:
You will get a response with status 500 Internal Server Error and the following content:

java.lang.NullPointerException
at java.util.concurrent.ConcurrentHashMap.hash(ConcurrentHashMap.java:333)
at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:988)
at org.kie.services.remote.cdi.DeploymentInfoBean.getRuntimeManager(DeploymentInfoBean.java:64)
at org.kie.services.remote.cdi.DeploymentInfoBean.getRuntimeEngine(DeploymentInfoBean.java:95)
at org.kie.services.remote.cdi.DeploymentInfoBean.getRuntimeEngineForTaskCommand(DeploymentInfoBean.java:72)
at org.kie.services.remote.rest.RestProcessRequestBean.doTaskOperationAndSerializeResult(RestProcessRequestBean.java:135)
at org.kie.services.remote.rest.RestProcessRequestBean$Proxy$$$_WeldClientProxy.doTaskOperationAndSerializeResult(RestProcessRequestBean$Proxy$$$_WeldClientProxy.java)
at org.kie.services.remote.rest.TaskResource.taskId(TaskResource.java:167)
at org.kie.services.remote.rest.TaskResource$Proxy$$$_WeldClientProxy.taskId(TaskResource$Proxy$$$_WeldClientProxy.java)
at sun.reflect.GeneratedMethodAccessor340.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:167)
at org.jboss.resteasy.core.ResourceMethod.invokeOnTarget(ResourceMethod.java:269)
at org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:227)
at org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:216)
at org.jboss.resteasy.core.SynchronousDispatcher.getResponse(SynchronousDispatcher.java:542)
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:524)
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:126)
at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:208)
at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:55)
at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:50)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:295)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.jboss.solder.servlet.exception.CatchExceptionFilter.doFilter(CatchExceptionFilter.java:65)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:246)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.jboss.solder.servlet.event.ServletEventBridgeFilter.doFilter(ServletEventBridgeFilter.java:74)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:246)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.jbpm.designer.web.filter.impl.PluggableFilter.doFilter(PluggableFilter.java:70)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:246)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.uberfire.security.server.UberFireSecurityFilter.doFilter(UberFireSecurityFilter.java:266)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:246)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:149)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:407)
at org.jboss.as.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50)
at org.jboss.as.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50)
at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:169)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:145)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:97)
at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:408)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:102)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:336)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:653)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:920)
at java.lang.Thread.run(Thread.java:744)

Expected results:
There should be a response with status 200 containing task details.

Additional info:
It is not possible to do any action with this kind of task like claiming or completing it.