"Fix" weird editor error with cinemachine

WIll have to look into why this fails in the first place

Author: Chman

PostProcessing/Editor/EffectListEditor.cs

@@ -126,6 +126,9 @@ public void Clear()
 
         public void OnGUI()
         {
+            if (m_Asset == null)
+                return;
+
             if (m_Asset.isDirty)
             {
                 RefreshEditors();