[FIX] web: prevent virtual datapoint creation when no default value

Previously, it used to create a virtual datapoint even though there was
no change on this field. If the field was a many2one, this datapoint
triggered a name_get call afterwards, but giving the virtual id of
the datapoint since there is no real record. The solution is to avoid
creating a virtual datapoint when it is not needed at all, thus fixing
the wrong name_get call.

Steps to reproduce the bug:
- Enable lots in Iventory
- Choose a product which is a component of another (through mrp bom)
- Set this product as tracked by lot
- Set this product inventory quantity to 0
- Create a new manufacturing order for the product for which it is a
  component
- Click on "Check Availability"
- Click on Produce
- You'll get an error as the web client tries to fetch the name_get of
  this datapoint even though the record does not exist.

1 files changed, 3 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 966a6ef3a78..fc3b68eeab7 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -2877,6 +2877,9 @@ var BasicModel = AbstractModel.extend({
 
                                 r._changes = _.defaults(value[2], r.data);
                                 for (var name in r._changes) {
+                                    if (r._changes[name] === null) {
+                                        continue;
+                                    }
                                     var isFieldInView = name in r.fields;
                                     if (isFieldInView && r.fields[name].type === 'many2one') {
                                         var rec = self._makeDataPoint({