Getting NullPointerException during BulkExport as .docx

While trying to do bulk export with about 30 issues as .docx Document and my own template, I get the following NullPointerException printed in my output document:

We are sorry, an unexpected error has occured in the export of your issue.
Please provide the information below to our support.

General Exception: java.lang.NullPointerException
java.lang.NullPointerException
at com.atlassian.jira.issue.customfields.impl.AbstractSingleFieldType.getValueFromIssue(AbstractSingleFieldType.java:71)
at com.atlassian.jira.issue.fields.ImmutableCustomField.getValue(ImmutableCustomField.java:349)
at com.xpandit.jiraxporter.exporter.d.a(Unknown Source)
at com.xpandit.jiraxporter.exporter.d.a(Unknown Source)
at com.xpandit.jiraxporter.exporter.c.convert(Unknown Source)
at com.xpandit.jiraxporter.component.service.XporterServiceImpl.exportMultipleIssues(Unknown Source)
at com.xpandit.jiraxporter.component.service.XporterServiceImpl.generateBulkExportReport(Unknown Source)
at com.xpandit.jiraxporter.component.a.b.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)