update config file

conf/vanilla/autoload_configs/conference_layouts.conf.xml

@@ -344,7 +344,7 @@
 	<image x="0" y="0" scale="360" floor-only="true"/>
 	<image x="180" y="180" scale="180" overlap="true" reservation_id="presenter"/>
       </layout>
-      <layout name="overlaps" auto-3d-position="true">
+      <layout name="overlaps" auto-3d-position="true" floor-only="true">
 	<image x="0" y="0" scale="360"/>
 	<image x="300" y="300" scale="60" overlap="true"/>
 	<image x="240" y="300" scale="60" overlap="true"/>