EXPORT FAILED for plp/ple if some of included cohorts was removed

[KSadomtsev]

WebAPI 2.8

Steps:
1)Create a plp/ple analysis
2)Add some cohorts to design
3)Remove one of the cohort from atlas(Request URL: WebAPI/cohortdefinition/181
Request Method: DELETE)
4)try to export Ple/PLP or download Study Package

Expected:
The cohort will remove from designs or we will see some information on the messages tab

Actual:

Request URL:WebAPI/estimation/78/export
Request Method: GET
Status Code: 500

Response:
{"payload":{"cause":null,"stackTrace":[],"message":"An exception occurred: java.lang.reflect.UndeclaredThrowableException","localizedMessage":"An exception occurred: java.lang.reflect.UndeclaredThrowableException","suppressed":[]},"headers":{"id":"c1447c41-936c-afe1-852d-258a31a9a45e","timestamp":1605780921710}}

Log:
2020-11-19 10:08:58.192 ERROR http-nio-8080-exec-1 org.ohdsi.webapi.util.GenericExceptionMapper - - java.lang.reflect.UndeclaredThrowableException at com.sun.proxy.$Proxy253.exportAnalysis(Unknown Source) at org.ohdsi.webapi.estimation.EstimationController.exportAnalysis(EstimationController.java:154) at org.ohdsi.webapi.estimation.EstimationController$$FastClassBySpringCGLIB$$71f94499.invoke(<generated>) at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:667) at org.ohdsi.webapi.estimation.EstimationController$$EnhancerBySpringCGLIB$$6230433b.exportAnalysis(<generated>) at sun.reflect.GeneratedMethodAccessor935.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)