Fixed the compound detector which needs to be first.

• The compound subdetector assembly needs to be defined before the named detectors.

topside/silicon_tracker.xml

@@ -134,6 +134,17 @@
 
   <detectors>
 
+    <detector id="SiTrackerSubAssembly_ID" 
+      name="SiTrackerSubAssembly" 
+      type="DD4hep_SubdetectorAssembly" 
+      vis="SiTrackerSubAssemblyVis">
+      <!--<shape name="SiTrackerVolume" type="Tube" rmin="SiliconTrackerMinR1" rmax="SiliconTrackerOuterRadius" dz="SiliconTrackerOuterBarrelLength/2.0 + 6*SiliconTrackerEndMod3RingDz" material="Air"/>
+      -->
+      <composite name="SiTrackerEndcapN"/>
+      <composite name="SiTrackerBarrel"/>
+      <composite name="SiTrackerEndcapP"/> 
+    </detector>
+
     <comment>
       Si Tracker Barrel
       Thiks barrel type was modified to have large modules.
@@ -846,16 +857,6 @@
       </layer>
     </detector>
 
-    <detector id="SiTrackerSubAssembly_ID" 
-      name="SiTrackerSubAssembly" 
-      type="DD4hep_SubdetectorAssembly" 
-      vis="SiTrackerSubAssemblyVis">
-      <!--<shape name="SiTrackerVolume" type="Tube" rmin="SiliconTrackerMinR1" rmax="SiliconTrackerOuterRadius" dz="SiliconTrackerOuterBarrelLength/2.0 + 6*SiliconTrackerEndMod3RingDz" material="Air"/>
-      -->
-      <composite name="SiTrackerEndcapN"/>
-      <composite name="SiTrackerBarrel"/>
-      <composite name="SiTrackerEndcapP"/> 
-    </detector>
   </detectors>
 
   <readouts>