Checklist PDF generation leads to exception when nbsp chars are in the item description

Error code: N6-E6 
Last business path:  https://testing.frentix.com/test6/url/RepositoryEntry/80019456/CourseNode/90522154611572 
Business path:  https://testing.frentix.com/test6/url/RepositoryEntry/80019456/CourseNode/90522154611581 
Date and time: 1/10/2019 12:02 PM
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<dispatchinfo>
<componentinfo>
<compname>ffo_main_assessment_list</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.course.nodes.cl.ui.CheckListAssessmentController</controllername>
<controllername>org.olat.course.nodes.cl.ui.CheckListRunForCoachController</controllername>
<controllername>org.olat.course.run.RunMainController</controllername>
<controllername>org.olat.course.run.CourseRuntimeController</controllername>
<controllername>org.olat.core.commons.fullWebApp.BaseFullWebappController</controllername>
</controllerinfo>
</dispatchinfo>
Throwable: java.lang.IllegalArgumentException

message:U+00A0 ('nbspace') is not available in this font Helvetica encoding: WinAnsiEncoding,java.lang.IllegalArgumentException

at org.apache.pdfbox.pdmodel.font.PDType1Font.encode(PDType1Font.java:426)
at org.apache.pdfbox.pdmodel.font.PDFont.encode(PDFont.java:324)
at org.apache.pdfbox.pdmodel.font.PDFont.getStringWidth(PDFont.java:353)
at org.olat.core.util.pdf.PdfDocument.addParagraph(PdfDocument.java:155)
at org.olat.core.util.pdf.PdfDocument.addParagraph(PdfDocument.java:135)
at org.olat.course.nodes.cl.ui.CheckedPDFExport.create(CheckedPDFExport.java:215)
at org.olat.course.nodes.cl.ui.CheckedPDFExport.create(CheckedPDFExport.java:186)
at org.olat.course.nodes.cl.ui.CheckListAssessmentController.doCheckedExportPDF(CheckListAssessmentController.java:639)
at org.olat.course.nodes.cl.ui.CheckListAssessmentController.formInnerEvent(CheckListAssessmentController.java:438)
at org.olat.core.gui.components.form.flexible.impl.FormBasicController.event(FormBasicController.java:421)