ofz#6764 Null-Dereference

Change-Id: Ic4c43d43b673f207123c99cbaca7efc019565c0d
Reviewed-on: https://gerrit.libreoffice.org/50820Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

xmloff/source/text/XMLTextMarkImportContext.cxx

@@ -291,7 +291,7 @@ void XMLTextMarkImportContext::EndElement()
                             m_rHelper.GetCursorAsRange()->getStart());
 
                         // check if beginning and end are in same XText
-                        if (xStartRange->getText() == xEndRange->getText())
+                        if (xStartRange.is() && xEndRange.is() && xStartRange->getText() == xEndRange->getText())
                         {
                             // create range for insertion
                             Reference<XTextCursor> xInsertionCursor =