That's a different issue and the latest code of your version on git seems a bit different from what you have. I will need the code you have to determine what's the problem there.
From what I see on git, there may be an issue in mod/dataform/field/_approve/field_patterns.php, with the following line:
if ($entry and $entry->approved) {
It is possible that $entry there in that particular use case doesn't have the approved property. If there is such a line in your code, try changing it to
if (!empty($entry->approved)) {
hth