Fix #29353 (#32151)

Hidden extrafields are NULL on update. Can only happen with extrafields in positions of commercial elements (facture, propal, commande, etc)

htdocs/core/class/commonobject.class.php

@@ -8210,6 +8210,10 @@ public function showOptionals($extrafields, $mode = 'view', $params = null, $key
 					if (($mode == 'create') && abs($visibility) != 1 && abs($visibility) != 3) {
 						continue; // <> -1 and <> 1 and <> 3 = not visible on forms, only on list
 					} elseif (($mode == 'edit') && abs($visibility) != 1 && abs($visibility) != 3 && abs($visibility) != 4) {
+						// We need to make sure, that the values of hidden extrafields are also part of $_POST. Otherwise, they would be empty after an update of the object. See also getOptionalsFromPost
+						$ef_name = 'options_' . $key;
+						$ef_value = $this->array_options[$ef_name];
+						$out .= '<input type="hidden" name="' . $ef_name . '" id="' . $ef_name . '" value="' . $ef_value . '" />' . "\n";
 						continue; // <> -1 and <> 1 and <> 3 = not visible on forms, only on list and <> 4 = not visible at the creation
 					} elseif ($mode == 'view' && empty($visibility)) {
 						continue;