ENGCOM-2793: [Forwardport] 6305 - Resolved product custom option title save issue #17607

 - Merge Pull Request #17607 from jignesh-baldha/magento2:2.3-develop-PR-port-15357
 - Merged commits:
   1. d60b3cf
   2. 71ce3fa
   3. 170d029
   4. 6aebfe8

Author: magento-engcom-team

app/code/Magento/Catalog/Model/Product/Option/Validator/DefaultValidator.php

@@ -106,7 +106,9 @@ protected function isValidOptionTitle($title, $storeId)
         if ($storeId > \Magento\Store\Model\Store::DEFAULT_STORE_ID && $title === null) {
             return true;
         }
-        if ($this->isEmpty($title)) {
+
+        // checking whether title is null and also changed is_empty to is_null
+        if ($title === null) {
             return false;
         }
 

app/code/Magento/Catalog/Model/ResourceModel/Product/Option/Value.php

@@ -256,7 +256,8 @@ protected function _saveValueTitles(AbstractModel $object)
                 $object->unsetData('title');
             }
 
-            if ($object->getTitle()) {
+            /*** Checking whether title is not null ***/
+            if ($object->getTitle()!= null) {
                 if ($existInCurrentStore) {
                     if ($storeId == $object->getStoreId()) {
                         $where = [

app/code/Magento/Sales/Model/Order/Pdf/Items/Invoice/DefaultInvoice.php

@@ -127,7 +127,8 @@ public function draw()
                     'feed' => 35,
                 ];
 
-                if ($option['value']) {
+                // Checking whether option value is not null
+                if ($option['value']!= null) {
                     if (isset($option['print_value'])) {
                         $printValue = $option['print_value'];
                     } else {

app/code/Magento/Sales/Model/Order/Pdf/Items/Shipment/DefaultShipment.php

@@ -89,7 +89,7 @@ public function draw()
                 ];
 
                 // draw options value
-                if ($option['value']) {
+                if ($option['value']!= null) {
                     $printValue = isset(
                         $option['print_value']
                     ) ? $option['print_value'] : $this->filterManager->stripTags(