aptkit: Fix UI freeze when the transaction is cancelled

usr/lib/linuxmint/mintUpdate/mintUpdate.py

@@ -2469,6 +2469,11 @@ def on_apt_install_finished(self, transaction=None, exit_state=None):
 
         self.finish_install(needs_refresh)
 
+    def on_apt_install_cancelled(self):
+        self.logger.write("Install cancelled")
+        self.set_status("", "", "mintupdate-updates-available-symbolic", True)
+        self.finish_install(False)
+
     @_async
     def finish_install(self, refresh_needed):
         try:
@@ -2572,6 +2577,7 @@ def install(self, widget):
                     self.logger.write("Ready to launch aptkit")
                     client = aptkit.simpleclient.SimpleAPTClient(self.ui_window)
                     client.set_finished_callback(self.on_apt_install_finished)
+                    client.set_cancelled_callback(self.on_apt_install_cancelled)
                     client.install_packages(self.packages)
                 else:
                     self.finish_install(False)