[FIX] web: properly handle onchanges after discard

When an onchange is resolved after a discard, it caused a traceback. We
now make sure that it does not happen.  Note: I think that the test is
quite neat.

1 files changed, 7 insertions, 0 deletions

diff --git a/addons/web/static/src/js/views/basic/basic_model.js b/addons/web/static/src/js/views/basic/basic_model.js
index b2c061f49e7..b4d343d7eb0 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -1049,6 +1049,13 @@ var BasicModel = AbstractModel.extend({
                 args: [idList, currentData, fields, onchange_spec, context],
             })
             .then(function (result) {
+                if (!record._changes) {
+                    // if the _changes key does not exist anymore, it means that
+                    // it was removed by discarding the changes after the rpc
+                    // to onchange. So, in that case, the proper response is to
+                    // ignore the onchange.
+                    return;
+                }
                 if (result.warning) {
                     self.trigger_up('warning', {
                         message: result.warning.message,