fix integrity issue

because django sets a foreign key constraint on sandbox_version_id
we may have issues if it refers to a version we want to delete

django/allgo/main/views.py

@@ -332,6 +332,11 @@ class WebappSandboxPanel(LoginRequiredMixin, TemplateView):
         webapp = self.get_object()
         action = request.POST["action"]
 
+        def stop_sandbox():
+            webapp.sandbox_state = Webapp.STOPPING
+            webapp.sandbox_version_id = None
+            webapp.save()
+
         log.info("action %r", request.POST["action"])
         if action == "start":
             if webapp.sandbox_state != Webapp.IDLE:
@@ -383,16 +388,14 @@ class WebappSandboxPanel(LoginRequiredMixin, TemplateView):
                         description=request.POST["description"],
                         url="http://WTF",
                         **extra)
-                webapp.sandbox_state = Webapp.STOPPING;
-                webapp.save()
+                stop_sandbox()
 
                 messages.success(request, "committing sandbox %r version %r"
                         % (webapp.name, number))
 
         elif action == "rollback":
             if webapp.sandbox_state == Webapp.RUNNING:
-                webapp.sandbox_state = Webapp.STOPPING
-                webapp.save()
+                stop_sandbox()
                 messages.success(request, "rolling back sandbox %r" % webapp.name)
             else:
                 messages.error(request, "unable to roll back, sandbox %r is not running"
@@ -400,8 +403,7 @@ class WebappSandboxPanel(LoginRequiredMixin, TemplateView):
 
         elif action == "abort":
             if webapp.sandbox_state == Webapp.START_ERROR:
-                webapp.sandbox_state = Webapp.STOPPING
-                webapp.save()
+                stop_sandbox()
                 messages.success(request, "reset sandbox %r" % webapp.name)
 
         elif action == "retry":
@@ -410,8 +412,7 @@ class WebappSandboxPanel(LoginRequiredMixin, TemplateView):
                 webapp.save()
                 messages.success(request, "starting sandbox %r" % webapp.name)
             elif webapp.sandbox_state == Webapp.STOP_ERROR:
-                webapp.sandbox_state = Webapp.STOPPING
-                webapp.save()
+                stop_sandbox()
                 messages.success(request, "stopping sandbox %r" % webapp.name)
 
         log.debug("new sandbox state: %r -> %r",