I can trigger import multiple times

15:20:14.602 [qtp2009787198-18] ERROR o.c.o.s.i.i.ProcessDefinitionXmlImportService - error while writing process definitions to elasticsearch
java.util.concurrent.ExecutionException: org.elasticsearch.action.ActionRequestValidationException: Validation Failed: 1: no requests added;
        at org.elasticsearch.common.util.concurrent.BaseFuture$Sync.getValue(BaseFuture.java:262)
        at org.elasticsearch.common.util.concurrent.BaseFuture$Sync.get(BaseFuture.java:249)
        at org.elasticsearch.common.util.concurrent.BaseFuture.get(BaseFuture.java:91)
        at org.camunda.optimize.service.es.writer.ProcessDefinitionWriter.importProcessDefinitionXmls(ProcessDefinitionWriter.java:55)
        at org.camunda.optimize.service.importing.impl.ProcessDefinitionXmlImportService.executeImport(ProcessDefinitionXmlImportService.java:33)
        at org.camunda.optimize.service.importing.ImportServiceHandler.executeProcessEngineImport(ImportServiceHandler.java:21)
        at org.camunda.optimize.rest.ProcessEngineImportRestService.importDataFromEngine(ProcessEngineImportRestService.java:20)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)