Index: /trunk/src/VBox/Main/xml/SettingsConverter.xsl
===================================================================
--- /trunk/src/VBox/Main/xml/SettingsConverter.xsl	(revision 15997)
+++ /trunk/src/VBox/Main/xml/SettingsConverter.xsl	(revision 15998)
@@ -664,5 +664,5 @@
          differs from the default (VDI) and otherwise simply delete it to let
          VBoxSVC set the correct new default value -->
-    <xsl:if test="not(translate(@defaultVDIFolder,'vdi','VDI')='VDI')">
+    <xsl:if test="@defaultVDIFolder and not(translate(@defaultVDIFolder,'vdi','VDI')='VDI')">
       <xsl:attribute name="defaultHardDiskFolder">
         <xsl:value-of select="@defaultVDIFolder"/>