Prevent GC allocation when popup doesnt need to be recreated

com.unity.shadergraph/Editor/Drawing/Controls/ChannelEnumControl.cs

         PopupField<string> m_PopupField;
         string[] m_ValueNames;
 
+        int m_PreviousChannelCount = -1;
+
         public ChannelEnumControlView(string label, int slotId, AbstractMaterialNode node, PropertyInfo propertyInfo)
         {
             AddStyleSheetPath("Styles/Controls/ChannelEnumControlView");
 
         void CreatePopup()
         {
+            int channelCount = SlotValueHelper.GetChannelCount(m_Node.FindSlot<MaterialSlot>(m_SlotId).concreteValueType);
+
+            {
+                if(channelCount == m_PreviousChannelCount)
+                    return;
+
+            }
-            int channelCount = SlotValueHelper.GetChannelCount(m_Node.FindSlot<MaterialSlot>(m_SlotId).concreteValueType);
+            m_PreviousChannelCount = channelCount;
-            m_PopupField = new PopupField<string>(popupEntries, (int)m_PropertyInfo.GetValue(m_Node, null));
+            var value = (int)m_PropertyInfo.GetValue(m_Node, null);
+            if(value >= channelCount)
+                value = 0;
+
+            m_PopupField = new PopupField<string>(popupEntries, value);
             m_PopupField.OnValueChanged(OnValueChanged);
             Add(m_PopupField);
         }