Exporting Calendar in iCal format results in error log when issue has no assignee

url: /plugins/servlet/calendar; user: admin ERROR admin 598x43020x1 1ikylau 172.29.221.204,10.227.133.74 /plugins/servlet/calendar [c.a.j.e.calendar.model.CalendarFactory] CalendarFactory.createCalendarIssue(Issue):Component Error creating attendee.
java.lang.NullPointerException
    at com.atlassian.jira.ext.calendar.model.CalendarFactory.getAttendee(CalendarFactory.java:284)
    at com.atlassian.jira.ext.calendar.model.CalendarFactory.createCalendarIssue(CalendarFactory.java:187)
    at com.atlassian.jira.ext.calendar.model.CalendarFactory.mapIssuesAsEvents(CalendarFactory.java:111)
    at com.atlassian.jira.ext.calendar.model.CalendarFactory.createICalendarFromSearch(CalendarFactory.java:71)
    at com.atlassian.jira.ext.calendar.ICalendarServlet.service(ICalendarServlet.java:109)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
    at com.atlassian.plugin.servlet.DelegatingPluginServlet.service(DelegatingPluginServlet.java:37)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
    at com.atlassian.plugin.servlet.ServletModuleContainerServlet.service(ServletModuleContainerServlet.java:49)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
    ... 48 filtered
    at com.atlassian.jira.plugin.mobile.web.filter.MobileAppRequestFilter.doFilter(MobileAppRequestFilter.java:59)
    ... 4 filtered
    at com.atlassian.jira.plugin.mobile.login.MobileLoginSuccessFilter.doFilter(MobileLoginSuccessFilter.java:54)
    ... 3 filtered
    at com.atlassian.diagnostics.internal.platform.monitor.http.HttpRequestMonitoringFilter.doFilter(HttpRequestMonitoringFilter.java:54)
    ... 8 filtered
    at com.atlassian.web.servlet.plugin.request.RedirectInterceptingFilter.doFilter(RedirectInterceptingFilter.java:21)
    ... 48 filtered
    at com.atlassian.oauth2.scopes.web.ReadWriteScopeFilter.doFilter(ReadWriteScopeFilter.java:46)
    ... 3 filtered
    at com.atlassian.troubleshooting.thready.filter.AbstractThreadNamingFilter.doFilter(AbstractThreadNamingFilter.java:46)
    ... 17 filtered
    at com.atlassian.jira.security.JiraSecurityFilter.lambda$doFilter$0(JiraSecurityFilter.java:66)
    ... 1 filtered
    at com.atlassian.jira.security.JiraSecurityFilter.doFilter(JiraSecurityFilter.java:64)
    ... 16 filtered
    at com.atlassian.pats.web.filter.TokenBasedAuthenticationFilter.doFilter(TokenBasedAuthenticationFilter.java:82)
    ... 3 filtered
    at com.atlassian.oauth2.provider.core.web.AccessTokenFilter.doFilter(AccessTokenFilter.java:82)
    ... 23 filtered
    at com.atlassian.jira.servermetrics.CorrelationIdPopulatorFilter.doFilter(CorrelationIdPopulatorFilter.java:30)
    ... 5 filtered
    at com.atlassian.plugins.authentication.sso.web.filter.loginform.DisableNativeLoginAuthFilter.doFilter(DisableNativeLoginAuthFilter.java:55)
    ... 3 filtered
    at com.atlassian.plugins.authentication.basicauth.filter.DisableBasicAuthFilter.doFilter(DisableBasicAuthFilter.java:70)
    ... 3 filtered
    at com.atlassian.jwt.internal.servlet.JwtAuthFilter.doFilter(JwtAuthFilter.java:37)
    ... 8 filtered
    at com.atlassian.web.servlet.plugin.request.RedirectInterceptingFilter.doFilter(RedirectInterceptingFilter.java:21)
    ... 4 filtered
    at com.atlassian.troubleshooting.thready.filter.AbstractThreadNamingFilter.doFilter(AbstractThreadNamingFilter.java:46)
    ... 3 filtered
    at com.atlassian.web.servlet.plugin.LocationCleanerFilter.doFilter(LocationCleanerFilter.java:36)
    ... 29 filtered
    at com.atlassian.jira.servermetrics.MetricsCollectorFilter.doFilter(MetricsCollectorFilter.java:25)
    ... 25 filtered
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:829)