NPE during bootstrap when a combine delta contains an autocreated property

For instance the following delta:
<?xml version="1.0" encoding="UTF-8"?><sv:node xmlns:sv="http://www.jcp.org/jcr/sv/1.0" xmlns:esv="http://www.onehippo.org/jcr/xmlimport" sv:name="hippo:configuration" esv:merge="combine">
<sv:node sv:name="hippo:update" esv:merge="combine">
<sv:property sv:name="hippo:lockExpirationTime" sv:type="Date">
<sv:value>2015-04-29T17:32:57.500+02:00</sv:value>
</sv:property>
</sv:node>
</sv:node>

Imported with the following initialize item:
<sv:node sv:name="gettingstarted-hippo-configuration">
<sv:property sv:name="jcr:primaryType" sv:type="Name">
<sv:value>hippo:initializeitem</sv:value>
</sv:property>
<sv:property sv:name="hippo:sequence" sv:type="Double">
<sv:value>30000.3</sv:value>
</sv:property>
<sv:property sv:name="hippo:contentresource" sv:type="String">
<sv:value>configuration.xml</sv:value>
</sv:property>
<sv:property sv:name="hippo:contentroot" sv:type="String">
<sv:value>/</sv:value>
</sv:property>
</sv:node>