Plugin requires diagram section, if not KotlinNullPointerException is generated

[v20stepanenko]

Currently, the plugin requires bpmndi:BPMNDiagram section in XML file as it provides an element layout. Typically this section is created by all modelers (Activiti, Camunda, Flowable) that are covered by this plugin. This section is not necessary for BPMN Engine to work as the element graph is provided in section. Unfortunately, creating a visually appealing layout on the fly is a complicated task (see i.e. the complexity of GraphViz + PlantUML). Therefore it will not be handled in the foreseeable future unless a pure Java element layout library will be found.

Original issue description:

I just started with your plugin and want to use it with our activiti files.

But at the first usage, I have this exception:

kotlin.KotlinNullPointerException
at com.valb3r.bpmn.intellij.plugin.activiti.parser.ActivitiParser.toProcessObject(ActivitiParser.kt:636)
at com.valb3r.bpmn.intellij.plugin.activiti.parser.ActivitiParser.parse(ActivitiParser.kt:149)
at com.valb3r.bpmn.intellij.plugin.core.CanvasBuilder.build(CanvasBuilder.kt:52)
at com.valb3r.bpmn.intellij.plugin.core.BpmnPluginToolWindow.run(BpmnPluginToolWindow.kt:82)
at com.valb3r.bpmn.intellij.activiti.plugin.actions.ViewActivitiBpmnDiagramAction$actionPerformed$1.run(ViewActivitiBpmnDiagramAction.kt:25)
at com.intellij.openapi.wm.impl.ToolWindowManagerImpl$activateToolWindow$1.run(ToolWindowManagerImpl.kt:632)
at com.intellij.openapi.application.TransactionGuardImpl.runWithWritingAllowed(TransactionGuardImpl.java:218)
at com.intellij.openapi.application.TransactionGuardImpl.access$200(TransactionGuardImpl.java:21)
at com.intellij.openapi.application.TransactionGuardImpl$2.run(TransactionGuardImpl.java:200)
at com.intellij.openapi.application.impl.ApplicationImpl.runIntendedWriteActionOnCurrentThread(ApplicationImpl.java:781)
at com.intellij.openapi.application.impl.ApplicationImpl.lambda$invokeLater$4(ApplicationImpl.java:319)
at com.intellij.openapi.application.impl.FlushQueue.doRun(FlushQueue.java:84)
at com.intellij.openapi.application.impl.FlushQueue.runNextEvent(FlushQueue.java:133)
at com.intellij.openapi.application.impl.FlushQueue.flushNow(FlushQueue.java:46)
at com.intellij.openapi.application.impl.FlushQueue$FlushNow.run(FlushQueue.java:189)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:776)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:727)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:746)
at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.java:969)
at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:839)
at com.intellij.ide.IdeEventQueue.lambda$dispatchEvent$8(IdeEventQueue.java:449)
at com.intellij.openapi.progress.impl.CoreProgressManager.computePrioritized(CoreProgressManager.java:808)
at com.intellij.ide.IdeEventQueue.lambda$dispatchEvent$9(IdeEventQueue.java:448)
at com.intellij.openapi.application.impl.ApplicationImpl.runIntendedWriteActionOnCurrentThread(ApplicationImpl.java:781)
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:496)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

I work with IntellIJ 2021.1.1 Ultimate edition on a windows 10 laptop