dont attempt to delete selected node if it is not a valid deletion target. resolves #1004

CHANGELOG.TXT

@@ -2,6 +2,7 @@
 
 Fixes:
 ------
+#1004: Duplicating root or PuTTy node through hotkey causes unhandled exception
 #1002: Disabling filtering without clearing keyword leaves filtered state
 #1001: Connection tree context menu hotkeys stop working and disappear in some cases
 #999: Some hotkeys stop working if File menu was called when PuTTy Saved Sessions was selected

mRemoteV1/UI/Controls/ConnectionTree/ConnectionTree.cs

@@ -281,6 +281,10 @@ namespace mRemoteNG.UI.Controls
 
         public void DuplicateSelectedNode()
         {
+            var selectedNodeType = SelectedNode.GetTreeNodeType();
+            if (selectedNodeType != TreeNodeType.Connection && selectedNodeType != TreeNodeType.Container)
+                return;
+
             var newNode = SelectedNode.Clone();
             SelectedNode.Parent.AddChildBelow(newNode, SelectedNode);
             newNode.Parent.SetChildBelow(newNode, SelectedNode);