ensure only one copy of stats shown, and close with collection

aqt/__init__.py

@@ -44,11 +44,12 @@ from anki.utils import checksum
 class DialogManager:
 
     def __init__(self):
-        from aqt import addcards, browser, editcurrent
+        from aqt import addcards, browser, editcurrent, stats
         self._dialogs = {
             "AddCards": [addcards.AddCards, None],
             "Browser": [browser.Browser, None],
             "EditCurrent": [editcurrent.EditCurrent, None],
+            "DeckStats": [stats.DeckStats, None]
         }
 
     def open(self, name, *args):

aqt/main.py

@@ -734,7 +734,7 @@ title="%s" %s>%s</button>''' % (
         deck = self._selectedDeck()
         if not deck:
             return
-        aqt.stats.DeckStats(self)
+        aqt.dialogs.open("DeckStats", self)
 
     def onPrefs(self):
         import aqt.preferences

aqt/stats.py

@@ -42,8 +42,12 @@ class DeckStats(QDialog):
         self.show()
         self.activateWindow()
 
+    def canClose(self):
+        return True
+
     def reject(self):
         saveGeom(self, self.name)
+        aqt.dialogs.close("DeckStats")
         QDialog.reject(self)
 
     def _imagePath(self):