bug #5449 Ensure that the entity is updated. (yceruto)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes #5449).

Discussion
----------

Ensure that the entity is updated.

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | All
| Fixed tickets | #5448

Commits
-------

f44cccf Ensure that the entity is updated.

cookbook/doctrine/file_uploads.rst

@@ -494,6 +494,7 @@ property, instead of the actual filename::
             if (is_file($this->getAbsolutePath())) {
                 // store the old name to delete after the update
                 $this->temp = $this->getAbsolutePath();
+                $this->path = null;
             } else {
                 $this->path = 'initial';
             }