fix some memory leaks

aqt/addcards.py

@@ -190,6 +190,7 @@ question on all cards."""), help="AddItems")
         saveGeom(self, "add")
         aqt.dialogs.close("AddCards")
         QDialog.reject(self)
+        self.deleteLater()
 
     def canClose(self):
         if (self.forceClose or self.editor.fieldsAreBlank() or

aqt/browser.py

@@ -471,6 +471,7 @@ class Browser(QMainWindow):
         self.teardownHooks()
         self.mw.maybeReset()
         evt.accept()
+        self.deleteLater()
 
     def canClose(self):
         return True

aqt/editcurrent.py

@@ -64,6 +64,7 @@ class EditCurrent(QDialog):
         self.mw.moveToState("review")
         saveGeom(self, "editcurrent")
         aqt.dialogs.close("EditCurrent")
+        self.deleteLater()
 
     def canClose(self):
         return True

aqt/stats.py

@@ -45,6 +45,7 @@ class DeckStats(QDialog):
     def reject(self):
         saveGeom(self, self.name)
         QDialog.reject(self)
+        self.deleteLater()
 
     def browser(self):
         name = time.strftime("-%Y-%m-%d@%H-%M-%S.png",