added null protection

source/FrameRecorder/Core/Editor/InputEditor.cs

@@ -6,11 +6,12 @@ namespace UnityEditor.FrameRecorder
     {
         public delegate EFieldDisplayState IsFieldAvailableDelegate(SerializedProperty property);
 
-        public IsFieldAvailableDelegate IsFieldAvailableForHost { get; set; }
+        public IsFieldAvailableDelegate isFieldAvailableForHost { get; set; }
 
         protected virtual void AddProperty(SerializedProperty prop, Action action )
         {
-            var state = IsFieldAvailableForHost(prop);
+            var state = isFieldAvailableForHost == null ? EFieldDisplayState.Disabled : isFieldAvailableForHost(prop);
+
             if (state == EFieldDisplayState.Enabled)
                 state = IsFieldAvailable(prop);
             if (state != EFieldDisplayState.Hidden)

source/FrameRecorder/Core/Editor/RecorderEditor.cs

@@ -32,7 +32,7 @@ namespace UnityEditor.FrameRecorder
 
                     editor = Editor.CreateEditor(m_SettingsObj);
                     if (editor is InputEditor)
-                        (editor as InputEditor).IsFieldAvailableForHost = m_Validator;                
+                        (editor as InputEditor).isFieldAvailableForHost = m_Validator;                
                 }
             }