Adobe connect: cannot create a user without first name

2020-03-11 15:44:05.270 [ajp-nio2-8021-exec-6] ERROR OLATRuntimeException ^%^ I200570-J39849 ^%^ org.olat.core.logging.OLATRuntimeException
https://xyz.de/auth/BusinessGroup/3241050192/tooladobeconnect/0/Meeting/56
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:73.0) Gecko/20100101 Firefox/73.0

**RedScreen**
Null value on 0 position
<dispatchinfo>
	<componentinfo>
		<compname>ffo_main_meeting</compname>
		<compclass>org.olat.core.gui.components.form.flexible.impl.FormWrapperContainer</compclass>
		<extendedinfo>n/a</extendedinfo>
		<event>
			<class&gt;org.olat.core.gui.components.form.flexible.impl.FormEvent</class&gt;
			<command>done</command>
			<tostring>com:done,org.olat.core.gui.components.form.flexible.impl.FormEvent@2f23a1</tostring>
		</event>
	</componentinfo>
	<controllerinfo>
	<controllername>org.olat.modules.adobeconnect.ui.AdobeConnectMeetingController</controllername>
	<controllername>org.olat.modules.adobeconnect.ui.AdobeConnectRunController</controllername>
	<controllername>org.olat.group.ui.run.BusinessGroupMainRunController</controllername>
	<controllername>org.olat.core.commons.fullWebApp.BaseFullWebappController</controllername>
	</controllerinfo>
</dispatchinfo>
Caused by: java.lang.IllegalArgumentException: Null value on 0 position
at org.apache.cxf.jaxrs.impl.UriBuilderImpl.toStringList(UriBuilderImpl.java:830)
at org.apache.cxf.jaxrs.impl.UriBuilderImpl.queryParam(UriBuilderImpl.java:722)
at org.olat.modules.adobeconnect.manager.DFNprovider.createPrincipal(DFNprovider.java:95)
at org.olat.modules.adobeconnect.manager.AdobeConnectManagerImpl.getOrCreateUser(AdobeConnectManagerImpl.java:556)
at org.olat.modules.adobeconnect.manager.AdobeConnectManagerImpl.registerFor(AdobeConnectManagerImpl.java:355)
at org.olat.modules.adobeconnect.ui.AdobeConnectMeetingController.doRegister(AdobeConnectMeetingController.java:420)
at org.olat.modules.adobeconnect.ui.AdobeConnectMeetingController.formInnerEvent(AdobeConnectMeetingController.java:349)
at org.olat.core.gui.components.form.flexible.impl.FormBasicController.event(FormBasicController.java:430)
at org.olat.modules.adobeconnect.ui.AdobeConnectMeetingController.event(AdobeConnectMeetingController.java:316)
at org.olat.core.gui.control.DefaultController.dispatchEvent(DefaultController.java:206)
at org.olat.core.gui.components.AbstractComponent$1.run(AbstractComponent.java:240)
at org.olat.core.logging.activity.ThreadLocalUserActivityLoggerInstaller.runWithUserActivityLogger(ThreadLocalUserActivityLoggerInstaller.java:108)
at org.olat.core.gui.components.AbstractComponent.fireEvent(AbstractComponent.java:238)
at org.olat.core.gui.components.form.flexible.impl.FormWrapperContainer.fireFormEvent(FormWrapperContainer.java:131)
at org.olat.core.gui.components.form.flexible.impl.Form.fireFormEvent(Form.java:717)
at org.olat.core.gui.components.form.flexible.impl.elements.FormLinkImpl.dispatchFormRequest(FormLinkImpl.java:239)
at org.olat.core.gui.components.form.flexible.impl.FormItemImpl.doDispatchFormRequest(FormItemImpl.java:561)
at org.olat.core.gui.components.form.flexible.impl.Form.evalFormRequest(Form.java:296)
at org.olat.core.gui.components.form.flexible.impl.FormWrapperContainer.doDispatchRequest(FormWrapperContainer.java:100)
at org.olat.core.gui.components.AbstractComponent.dispatchRequest(AbstractComponent.java:193)
at org.olat.core.gui.components.Window.doDispatchToComponent(Window.java:1218)
at org.olat.core.gui.components.Window.dispatchRequest(Window.java:400)
... 39 more