Wait 300 milliseconds before tearDown to give the FlickerTLW's wx.CallLater

a chance to run, which avoids this exception:

wx/core.py, line 3096, in Notify
    self.result = self.callable(*self.args, **self.kwargs)
RuntimeError: wrapped C/C++ object of type Filling has been deleted

Ensure that the Crust object's "lastsashpos" attribute is defined to avoid this exception:

wx/py/crust.py", line 150, in SaveSettings
    if self.lastsashpos != -1:
AttributeError: 'Crust' object has no attribute 'lastsashpos'

unittests/test_lib_mixins_inspection.py

@@ -1,4 +1,5 @@
 import unittest
+import time
 import wx
 import wx.lib.mixins.inspection as wit
 
@@ -6,6 +7,26 @@ import wx.lib.mixins.inspection as wit
 
 class wit_TestCase(unittest.TestCase):
 
+    def tearDown(self):
+        '''
+        OnClose can trigger:
+            AttributeError: 'Crust' object has no attribute 'lastsashpos'
+         so we'll ensure that the InspectionFrame's crust has that attr.
+        '''
+        windows = wx.GetTopLevelWindows()
+        for window in windows:
+            if type(window) == wx.lib.inspection.InspectionFrame:
+                if hasattr(window, 'crust'):
+                    pass
+                    if not hasattr(window.crust, 'lastsashpos'):
+                        window.crust.lastsashpos = -1
+
+        # class _InspectionHighlighter's FlickerTLW method invokes
+        # wx.CallLater(300, self._Toggle, tlw),
+        # so let's give it a chance to run:
+        time.sleep(0.3)
+        super(wit_TestCase, self).tearDown()
+
     def test_App(self):
         app = wit.InspectableApp()