FlowchartWindow force clears filteredBlocks during target Flowchart change

- better handles switching scenes and to and from play mode
- warns user when nulls are found

Assets/Fungus/Scripts/Editor/FlowchartWindow.cs

@@ -336,6 +336,7 @@ namespace Fungus.EditorUtils
             if (flowchart == null)
             {
                 blocks = new Block[0];
+                filteredBlocks = new Block[0];
             }
             else
             {
@@ -347,6 +348,8 @@ namespace Fungus.EditorUtils
 
         protected virtual void OnInspectorUpdate()
         {
+            if (HandleFlowchartSelectionChange()) return;
+
             // Ensure the Block Inspector is always showing the currently selected block
             var flowchart = GetFlowchart();
             if (flowchart == null || AnyNullBLocks())
@@ -450,13 +453,22 @@ namespace Fungus.EditorUtils
             {
                 filterStale = false;
                 //reset all
-                foreach (var item in filteredBlocks)
+                for (int i = 0; filteredBlocks != null && i < filteredBlocks.Length; i++)
+                {
+                    if(filteredBlocks[i] != null)
+                    {
+                        filteredBlocks[i].IsFiltered = false;
+                    }
+                }
+
+                var nullCount = filteredBlocks.Count(x => x == null);
+                if (nullCount > 0 && nullCount != filteredBlocks.Length)
                 {
-                    item.IsFiltered = false;
+                    Debug.LogWarning("Null block found in filteredBlocks. May be a symptom of an underlying issue");
                 }
                 
                 //gather new
-                filteredBlocks = blocks.Where(block => block.BlockName.ToLower().Contains(searchString.ToLower())).ToArray();
+                filteredBlocks = blocks.Where(block => block.BlockName.IndexOf(searchString, StringComparison.OrdinalIgnoreCase) >= 0).ToArray();
                 
                 //update filteredness
                 foreach (var item in filteredBlocks)
@@ -573,9 +585,16 @@ namespace Fungus.EditorUtils
         {
             mouseDownSelectionState.AddRange(flowchart.SelectedBlocks);
             flowchart.ClearSelectedBlocks();
-            foreach (var item in mouseDownSelectionState)
+            for (int i = 0; i < mouseDownSelectionState.Count; i++)
             {
-                item.IsControlSelected = true;
+                if (mouseDownSelectionState[i] != null)
+                {
+                    mouseDownSelectionState[i].IsControlSelected = true;
+                }
+                else
+                {
+                    Debug.LogWarning("Null block found in mouseDownSelectionState. May be a symptom of an underlying issue");
+                }
             }
         }
 
@@ -633,6 +652,17 @@ namespace Fungus.EditorUtils
                 blockInspector = null;
                 prevFlowchart = flowchart;
                 executingBlocks.ClearAll();
+
+                //attempt to defilter previous, if due to scene change these will be null
+                //  the regular filter updates will still occur within UpdateBlockCollection
+                for (int i = 0; i < filteredBlocks.Length; i++)
+                {
+                    if (filteredBlocks[i] != null)
+                    {
+                        filteredBlocks[i].IsFiltered = false;
+                    }
+                }
+
                 UpdateBlockCollection();
                 Repaint();
                 return true;