Fix for bug # 76472 Assertion in GetChildAt() r=valeski sr=rpotts

xpfe/components/shistory/src/nsSHistory.cpp

@@ -728,6 +728,7 @@ nsSHistory::CompareSHEntry(nsISHEntry * aPrevEntry, nsISHEntry * aNextEntry, nsI
 	  
     prevContainer->GetChildAt(i, getter_AddRefs(pChild));
 	  nextContainer->GetChildAt(i, getter_AddRefs(nChild));
+    if (dsCount > 0)
 	    dsTreeNode->GetChildAt(i, getter_AddRefs(dsTreeItemChild));
 
 	  if (!dsTreeItemChild)