added early-exit in various BuildTree methods when window is closing

Author: pschraut

Editor/Scripts/GCHandlesView/GCHandlesControl.cs

@@ -105,6 +105,9 @@ public TreeViewItem BuildTree(PackedMemorySnapshot snapshot)
 
             for (int n = 0, nend = m_Snapshot.gcHandles.Length; n < nend; ++n)
             {
+                if (window.isClosing) // the window is closing
+                    break;
+
                 var gcHandle = m_Snapshot.gcHandles[n];
                 var managedTypeIndex = -1;
                 if (gcHandle.managedObjectsArrayIndex >= 0)

Editor/Scripts/ManagedHeapSectionsView/ManagedHeapSectionsControl.cs

@@ -93,6 +93,9 @@ public TreeViewItem BuildTree(PackedMemorySnapshot snapshot, PackedMemorySection
 
             for (int n = 0, nend = sections.Length; n < nend; ++n)
             {
+                if (window.isClosing) // the window is closing
+                    break;
+
                 var section = sections[n];
 
                 var item = new HeapSectionItem()

Editor/Scripts/ManagedTypesView/ManagedTypesControl.cs

@@ -71,6 +71,9 @@ public TreeViewItem BuildTree(PackedMemorySnapshot snapshot)
 
             for (int n = 0, nend = m_Snapshot.managedTypes.Length; n < nend; ++n)
             {
+                if (window.isClosing) // the window is closing
+                    break;
+
                 var type = m_Snapshot.managedTypes[n];
 
                 var item = new ManagedTypeItem

Editor/Scripts/StaticFieldsView/StaticFieldsControl.cs

@@ -108,6 +108,9 @@ public TreeViewItem BuildTree(PackedMemorySnapshot snapshot)
 
             for (int n = 0, nend = m_Snapshot.managedStaticTypes.Length; n < nend; ++n)
             {
+                if (window.isClosing) // the window is closing
+                    break;
+
                 var type = m_Snapshot.managedTypes[m_Snapshot.managedStaticTypes[n]];
 
                 var group = new StaticTypeItem